do you have any indication if this is just isModified() 

or if new content is checked against old content

Reason: in past isModified () just checked write access, not the content.
So a change from TRUE to FALSE and back to TRUE between %OpenId()  and %Save() was marked as change (false positive)

so this was finally dropped in favor of GetStored()
 

I know of i%PropName

where is  m%PropName documented?

all I found is:

Internally, Caché also uses additional instance variables with names such as r%PropName and m%PropName,
but these are not supported for direct use.

And no hint how they could be used.

but I doubt that XML Schema Wizard will do anything useful with a .dtd definition.

To use httpS://  in xml schema wizard you need to definde an  SSL configuration in  SMP  System > Security Management > SSL/TLS Configuration.

and your class should have class parameter DDL Allowed

Class PCD.NATION  Extends %Persistent [ DdlAllowed ]

1) install gbk character set table to your instance (if available)

??? ....\InterSystems\Cache\mgr\Locale\allmessages_zh-cn.xml ???

2) use  $zconvert()  to translate it.

if 1) fails you may trigger an external converter using $ZF(-2 ,....)

or use command pipe to run an external conversion. 

What error is "some" ?

Detailed description on ADD FOREIGN KEY

Look especially on

Go to the Management Portal, select [Home] > [Configuration] > [General SQL Settings]. View the current setting of
Allow DDL ADD Foreign Key Constraint When Foreign Key Exists.

my assumption; you have installed CSP Gateway on your public website 

Hint:
backup of %SYS is good for recovery but not  recommended for a copy
there a lot of instance related settings (e.g. config) included that may cause serious problems in the copy.

to verify your mailing is working correctly it is useful  to get the mail server in your hands
hMailServer is one of several others.

Here is a lot of information on Intersystems IRIS to reduce confusion.
Your InterSystems sales rep will have more.

contact your sales rep.

Laura,

there is something like .....     
Ens.Util.XML.Reader
especially   ##class(Ens.Util.XML.Reader).ObjectFromString(. . . )

But you have to fix ther error pointed out by @Eduard Lebedyuk anyhow