In your question and comment I see two tables iagentbySkillsetStat and iSkillsetStat. Are you sure that you working with right table which contains such property ?

If you have an access to WRC, you can get FieldTest versions, Caché and Ensemble with test license keys. If not I think you may ask for an account by sending email to support@intersystems.com

Whats the strange question?

Are you know meaning for two of this words ?

Caché - it's an InterSystems database, platform which you are working on

and cache -  which is just a technology, it is a bunch of ways hardware and software how to return previously accessed data more quickly 

To support Raspberry Pi, IntersSystems should support ARM, but not sure that so easy, and could be valuable for them, even if remember how quickly  they ended GlobalsDB. But GlobalsDB was a quite good product, and was used in some projects, and even still used. If somebody needs to use micro-pc they can use some alternatives on Intel's process such as Intel Galileo

What exactly do you want to reach, authentification in Caché using LDAP login, or you want to connect and load users from AD ?

Closing Tab in the browser, does nothing on the server side, because in simple way, browser only ask server by user's requests.

You can only do some ajax request just when user closes the page, to close session on the server side, no more.

Every session will be alive in their Timeout, that Timeout could be get by default from settings, or you can set it programmatically ( set %session.AppTimeout=900), and only when timeout is exceeded the used grace period 5 minutes. And only after that session and license will be released. 

And you should remember, that if user closed tab, he can open it again, and it will be the same session as before.

Since so big difference between this versions, and you may caught many incompatibilities, I would very recommend to install  new instance and move all your data and settings from the old one. And then check everything in your application very carefully.

Such error you can face on a windows as well. Your super port has already in use by another instance of Cache. And you can change port for new instance, by editing cache.cpf file in the root of installed Cache. 

To be sure that port is in use you can use some network tools, such as netstat

netstat -na | grep 1972
tcp4       0      0  *.1972                *.*                    LISTEN

or lsof, which can show which process with pid uses this port

sudo lsof -i tcp:1972
cache   14960 cacheusr    4u  IPv4 0x768e107dffb0f4df      0t0  TCP *:1972 (LISTEN)

You can use $order to order all users, in global

set FF=""
for {
  set FF = $order(^Users(FF))
  quit:FF=""
  set isAllowed = $get(^Users(FF, "SETTINGS", "isAllowed"))
  write:isAllowed !,"User ",FF," is allowed"
}

As I remember, you could create user TRM or TELNET, with routine %PMODE, and will get access without authentication.

Don't remember how it was in 5.0, but currently default login/password is _SYSTEM/SYS

UDL format is for classes only, and this format how that classes looks in Studio.

Export web files, available as any others in XML format with $system.OBJ.Export()

USER>d $system.OBJ.Export("/csp/user/*.*","export.xml")

Exporting to XML started on 08/24/2016 20:52:44
Exporting CSP/CSR or file: /csp/user/ML_Util.js
Exporting CSP/CSR or file: /csp/user/menu.csp
Exporting CSP/CSR or file: /csp/user/showsource.csp
Export finished successfully.

And all web files stores as files in the directory for this web-application, so you can get it directly, but native export/import works only in XML

You should not read stream which you got from request, just pass it to $fromJSON, because it understand streams too.

Documentation about $horolog 

Contains the local date and time for the current process.