I have another Microsoft account which has been accessed by someone else. They changed the...

Sorry but i cant access my account because my email address has been removed and someone else has put theirs on and changed passwords, etc

Unfortunately, MS don't allow you to change the primary email due to the risk of fraud, hacking and whatnot...if they allowed it, then a hacked account could then have it's address changed

I'm technically going to be "hacked", or someone else won't have access to Microsoft services.

As they're going to disable my account, any new student that comes and gets assigned to my handle (which is automatically generated through the users initials), anyone else can end up with the same login account as I do.

So someone else will have my email, at some period of time. Either I'll have to delete this @cin.ufpe.br account entirely, thus losing my game saves and purchases, or someone else owning the current handle will be unable to access Microsoft services, up to and including MSDN.

I just want to port everything to my current account, which has a similar handle. I fully understand the reason you pointed out, but there must be an exception for cases like these.

No one here would have access to your account to be able to do so. If someone else has access to your account, change the password.

It sounds like someone has had access to your old account somehow.

For the sake of any personal information you may have left registered on your old banned account, it is best to change the password so nobody else (but you) will have further access.

Change Microsoft Account password article:
support.xbox.com/.../change-microsoft-account-password

Hello, I have access to an account through which I used to log into minecraft premium, but now it logs me out of the account and writes that the email has been changed/deleted or does not match any account.

This whole situation is confusing because I had this account before the migration and was accessing the account using a different email address where I have Mojang messages.

The migration only added a way to log in, this account can now only be the information I used to log into the account. I can also provide old information from mojang, or regarding the account such as:

nicknames, emails from which the account was accessed, related phone numbers, answers to security questions on the mojang website.

I also have emails confirming the theft, such as:

MultiMC application has been linked to your Microsoft account,

A new login has been detected, your XBOX Live account has been moved from "country" to "country".

It seems to me that the account has already been sold to someone else, although I don't know if this is possible because "New login detected" referred to another "country" and your XBOX Live account has been moved from "country" to "country". Also a different country so the countries do not match.