Migrate to UCS5 - import users and computers

Hi. We are stuck on old UCS4 version, and old brand domain like site.oldcompanyname.com We have over 100 windows clients joined to our UCS4 AD.

I was wondering if it is possible to either:

A) install new UCS5, and import users and computers, keep same AD domain site.oldcompanyname.com we can change DNS IP.
Expected results: users can login as usual, no need to join new domain.

B) install new UCS5 with new domain name site.newname.com, import users and computers. we can change DNS IP.
Expected results: users can login as usual, no need to join new domain.

C) install new UCS5, join into existing domain with UCS4. Promote new UCS5 to primary.

Thanks in advance.

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