I'm sorry to say, but this kind of information is an essential part of the task, and as such should be written before the recurring "As usual, the shortest ..."

Also, it would be nice, if the output example would show this trivia (the invisible spaces)!

I just saw "input = 3" and the output showed no trailing blanks!

And I saw the Notice with two links
- how to compute the size
- test examples
I wasn't interested in opening them, first, I know how to compute code size and second, I make the examples myself.
Hiding information in a side notice is a questionable practice.

ClassMethod Pyramide(n)
{
	s a="#" f i=1:1:n w ?n-i,a,?2*n-1,! s a=a_"##"
}

For a test use

w $c(27)_"[7m" d ##class(your.class).Pyramide(5) w $c(27)_"[0m"

 and you should get   

The bad news is,
you have to be careful when you adapt delimited list to $list(). A stubborn change from a delimited list to $list() can become dangerous. The reason:

set $piece(var,del,1) = value // piece 1 of var is ALWAYS a string
set $list(var,1)      = value // listitem 1 is either a number or a string

kill x set $piece(x,",",1) = 100+1 write $zhex($p(x,",")) --> 257
kill x set $list(x,1)      = 100+1 write $zhex($li(x,1))  --> 65

kill x set $piece(x,",",1) = 100 write $zhex($p(x,",")) --> 256
kill x set $list(x,1)      = 100 write $zhex($li(x,1))  --> 64

kill x set $piece(x,",",1) = "100" write $zhex($p(x,",")) --> 256
kill x set $list(x,1)      = "100" write $zhex($li(x,1))  --> 256

In other words, $list() retains the type of the expression whereas $piece() always converts it to a string.

The good news is,
there are just a few situations, where this could cause a problem, to tell the truth, in a nutshell, I can only think of two possibilities: $zhex() and $zboolean(). But who knows, what a mad programmer accomplish...

If you want to reorder JSON properties (alphabetically or just put some of them at the beginning) then use a utility method, like this, especially if you have several object(types) to reorder

Class DC.Utility Extends %RegisteredObject
{
/// Reorder a JSON Object or Array
/// 
/// obj:  JSON-Object
/// 	  ord: prop1, prop2, ...	Desired order for (some) properties
/// 	       (Properties not listed are copied in the order in which they were created)
/// 	       If ord not present, properties will be reordered in aplphabetical order
/// 	       
/// obj: JSON-Array
/// 	 ord: pos1, pos2, ...	Desired order for (some) array items
/// 	      (Items not listed are copied in ascending order)
/// 	      
ClassMethod ReOrder(obj As %DynamicAbstractObject, ord... As %String)
{
	i obj.%Extends("%DynamicObject") {
		s new={}, itr=obj.%GetIterator()
		i '$g(ord) {
			while itr.%GetNext(.k) { s done(k)=0 }
			s k="" f  s k=$o(done(k)) q:k=""  d new.%Set(k,obj.%Get(k))
		} else {
			f i=1:1:$g(ord) { s k=ord(i),done(k)=1 d:$e(obj.%GetTypeOf(k),1,2)'="un" new.%Set(k,obj.%Get(k)) }
			while itr.%GetNext(.k,.v) { d:'$d(done(k)) new.%Set(k,v) }
		}
		
	} elseif obj.%Extends("%DynamicArray") {
		s new=[], itr=obj.%GetIterator(), max=obj.%Size(), done=""
		f i=1:1:$g(ord) { s k=ord(i) i k,k<=max d new.%Push(obj.%Get(k-1)) s $bit(done,k)=1 }
		while itr.%GetNext(.k,.v) { d:'$bit(done,k+1) new.%Push(v) }
		
	} else { s new=obj }
	
	q new
}
}

Some examples

s car={"color":"red", "fuel":"diesel", "maxspeed":150, "maker":"Audi", "model":"Quattro Q5", "power":300, "available":true, "rating":8, "allWheel":true }
s car1=##class(DC.Utility).ReOrder(car) // order all props alphabetically
s car2=##class(DC.Utility).ReOrder(car,"maker","model","available") // start with maker, model, etc.

w car.%ToJSON(),!,car1.%ToJSON(),!,car2.%ToJSON() --->
{"color":"red","fuel":"diesel","maxspeed":150,"maker":"Audi","model":"Quattro Q5","power":300,"available":true,"rating":8,"allWheel":true}
{"allWheel":"1","available":"1","color":"red","fuel":"diesel","maker":"Audi","maxspeed":150,"model":"Quattro Q5","power":300,"rating":8}
{"maker":"Audi","model":"Quattro Q5","available":"1","color":"red","fuel":"diesel","maxspeed":150,"power":300,"rating":8,"allWheel":"1"}

Is NOT the same. You can it prove by adding a label to the line with the read command and a new line at the end

    // DOT VERSION
    // Use fic
old Read *R:20 Else  Do  Quit    ;;;;  comando else aplicado a read.
    . Use 0 Write !!!,"Expired time."
    If $c(R)="a" d
    . Use 0 Write !!!,"A letter a has been read."
    . Quit
    write !,"If there are more lines, they will be executed",!
    quit

    // LITTLE BIT MODERN VERSION
    // Use fic
new Read *R:20
    If $Test {
    Use 0 Write !!!,"One character read"
    Quit
    }
    Else {
    Use 0 Write !!!,"Expired time."
    }
    write !,"If there are more lines, they will be executed",!
    quit
 

now let run both of them...

do old // let the timeout occur
do old // now with some input
do new // let the timeout occur
do new // now with some input

Do you see the difference? If there are more lines (at end) they will be executed in opposite cases (timeout/notimeout)

Things are not so easy as they seem, you have to consider scopes too. Take the above class (DC.LineNumber) and add three more methods:

ClassMethod CaseA(x)
{
    if x goto zTest
    quit "A0"
    
zTest quit "A1"
}

ClassMethod CaseB(x)
{
    if x goto Test
    quit "B0"
    
Test quit "B1"
}

ClassMethod Test()
{
    write ..CaseA(0),..CaseA(1) set linenumber=..SrcLineNumberFromStack(.routine,.label,.offset,.src) do prt
    write ..CaseB(1),..CaseB(0) set linenumber=..SrcLineNumberFromStack(.routine,.label,.offset,.src) do prt
    quit
    
    // debug
prt	write !,"routine: ",routine
    write !,"label: ",label
    write !,"offset: ",offset
    write !,"linenumber: ",linenumber
    write !,"src:",src,!!
}

and now do the test:

do ##class(DC.LineNumber).Test()

and check the output... 

OK, I know, this is a (very) constructed case and shouldn't coincide with an everyday development style, but who knows, what a mad programer sometimes produces...

If you have just a few breaks, one of the possible solutions has been given by Robert CemperIn case, you have tons of those breaks, you could execute the unit test in background:

job ^performUnitTest

assumed, your unittest can work in background and all the output goes, for example, in a file.

The solution for the case you let run the unittest in a terminal session, could be something like this

do turnOffBreaks, performUnitTest, turnOnBreaks

The only problem is, to turn breaks off (or on), you need one view command, one $view() function and one $zutil() function (to get the right address for the view-s). Unfortunatelly, the use of the above tools is discouraged, so your best bet is, to ask WRC for a help.

Are you sure,  ..ObjOrigem contains a VALID object reference? Your output shows just a string "%Library.DynamicObject". A valid OREF looks like "nn@%Library.DynamicObject". What is the output of $isobject(..ObjOrigem)?

Anyway, the $method(oref, "Propname"_"Get") works in IRIS, at least, in my IRIS 2021.2

USER>set obj={"Id":"myId"}
USER>write $property(obj,"Id")  --> myId
USER>write $method(obj,"IdGet") --> myId
USER>write $zv  -->  IRIS for UNIX (Ubuntu Server LTS for x86-64) 2021.2 (Build 649U) Thu Jan 20 2022 08:49:51 EST
USER>write obj  -->  5@%Library.DynamicObject

Oh, this is a misunderstanding. I thought, the screenshot is coming from a (not showed) link, and anticipated the link points to some ISC site.
Anyway, ChatGPT and other ChatBots (nowadays, they often pop up on various sites, mainly on those of big companies) tries to mimic a human and often end up only with an reference to FAQs or with a wrong (inappropriate) answer.
They all base upon AI (some says: AI=artificial intelligence, others say: AI=absent intelligence). My bottom line is, AI is for some areas already "usable" and for others, it still "will require some more time".

You can't access the class name alone

write $system.Version          // is just a class name, something like
write ##class(SYSTEM.Version)  // (hence both lines gives you a syntax error)

You have to specify a property or a method. Because $System.Version is an abstract class, you can specify a method only

write $system.Version.GetVersion()

Hope this clarifies things

To be honest, I was also impressed, but not about ChatGPT rather about the suggested solution!  I have no idea, who at ISC wrote this recommendation, but the five clicks on my IRIS-2021.1 end up in NOTHING. On the right-side panel I see 'System Information' but this can't be clicked, below is 'View System Dashboard', here you see everithing, except a version info. So dear ChatGPT, if someone asks you again, the (better) answer is:
- login to management portal
- click on 'About' (here you see the version and much much more)
This works for all IRIS versions (until now) and for all Cache versions which have a Management Portal. For the older (over 20 years) Cache versions right-click on the cube and select 'Config Manager' (on Windows, of course. In that times, I didn't worked on other platforms, hence no advices).

First, the suggestion of Victor Gordillo  is correct.

do ##class(Some.Class).%BuildIndices()

solves most index related problems.

Second, there are a couple of things, we do not know, but you
- did you made an in-place-upgrade or a clean install + data transfer
- the class in question is the same on IRIS and Cache (i.e. no change was made)
- is the class re-compiled (on IRIS)
- what do you exactly mean when you say "Not opening an instance...": (1) you get an NULL-OREF or (2) you get an error
- what do you provide as a NULL value: (1) "", (2) $c(0), (3) " " or something else as open parameter

A shortened class definition (we don't need the whole definition) would be also helpfull, something like this

Class Problem.Class extends %Persistent
{
Property Field1 as %String;
Property Filed2 As %String;

Index composite on (Field1, Field2) [ Unique];
}

If your serial class is named Data.Serial (as in your example code) then you should use the same name for the serial property too

Class Data.Persistent Extends %Persistent
{
Property MPID as %Integer;
Property Name as Data.Serial;   <--- !!!!!
}

The correct way to set the values

Set Obj=##Class(Data.Persistent).%New()
Set Obj.MPID=MPID
Set Obj.Name.FirstName=FirstName   ; <----
Set Obj.Name.LastName=LastName     ; <----
Set tSC=Obj.%Save()

I think, I have a solution for you

ClassMethod GetImage()
{
	s req=##class(%Net.HttpRequest).%New()
	s req.Server="www.distrelec.de"
	s req.SSLConfiguration="SSL"
	s req.ReadRawMode=1        //  <<---- this is your solution
	d req.Get("/Web/WebShopImages/landscape_medium/_t/if/sortimentsboxen-1.jpg")
	q req.HttpResponse
}

To get the image

s rsp=##class(Some.Class).GetImage()
i rsp.StatusCode=200 {
    s file="c:\temp\imageName.jpg"
    o file:"nwu":0
    i $t u file d rsp.Data.Rewind(),rsp.Data.OutputToDevice()
    c file
}

 That's all...

To download that image, you need just a few lines of code

Class Some.Class Extends %RegisteredObject
{
ClassMethod GetImage()
{
	s req=##class(%Net.HttpRequest).%New()
	s req.Server="www.distrelec.de"
	s req.SSLConfiguration="SSL" // use your SSL-Config-Name
	d req.Get("/Web/WebShopImages/landscape_medium/_t/if/sortimentsboxen-1.jpg",1)
	q req.HttpResponse
}
}

So your code is more or less OK, but the rest of the process is ominous

set rsp=##class(Some.Class).GetImage()
zw rsp
rsp=7@%Net.HttpResponse  ; <OREF>
+----------------- general information ---------------
|      oref value: 7
|      class name: %Net.HttpResponse
| reference count: 3
+----------------- attribute values ------------------
|    ContentBoundary = ""
|        ContentInfo = "charset=UTF-8"
|      ContentLength = 17759
|        ContentType = "image/jpeg;charset=UTF-8"
|               Data = "8@%Stream.GlobalCharacter"
|Headers("CACHE-CONTROL") = "max-age=0"
|Headers("CONTENT-LENGTH") = 17759
|Headers("CONTENT-TYPE") = "image/jpeg;charset=UTF-8"
|    Headers("DATE") = "Mon, 14 Nov 2022 10:57:10 GMT"
|    Headers("ETAG") = "a919e895229c7883864aecbfa2717516"
|Headers("LAST-MODIFIED") = "Thu, 01 Jan 1970 00:00:01 GMT"
|Headers("SET-COOKIE") = "visid_incap_2373370=1U8JalxbRJOzRFviQpi05AYfcmMAAAAAQUIPAAAAAADRm"
|Headers("STRICT-TRANSPORT-SECURITY") = "max-age=31536000; includeSubDomains; preload"
|   Headers("X-CDN") = "Imperva"
| Headers("X-IINFO") = "5-19652015-0 0CNN RT(1668423430526 51) q(0 -1 -1 0) r(0 -1)"
|        HttpVersion = "HTTP/1.1"
|       ReasonPhrase = "OK"
|         StatusCode = 200
|         StatusLine = "HTTP/1.1 200 OK"
+-----------------------------------------------------

The sender says, content type is "image/jpeg", which is OK, but charset=UTF-8 is, I think, a problem. A jpeg-image usually starts with (hex) bytes:

FF D8 FF E0 00 10 4A 46 49 46 ...

The HTTP-Response gives us

do rsp.Data.Rewind()
zzdump rsp.Data.Read(10)

3F 3F 3F 10 4A 46 49 46 00 01                           ???.JFIF..

But I'm in no way a web-expert, but it seems to me, Cache tries to decode (according to content-type =image/jpg; charset=UTF-8) the incomming raw (jpeg) data. The first byte, FF, will already give an error (no utf-8 encoded byte can start with FF) and returns an "?" char as a replacement. The next two "?" (hex: 3F) chars are also arised from (inpossible) decoding. Why the same page works, if you try it with Chrome or Firefox: I think, they either ignore the charset=UTF-8 or just show the raw data after the first decoding error.