C++Builder 12 Update 1: Migrating project, compiler versions

[BuilderFox 0]

A very first Hello and many thanks for all your efforts,

 

I'm trying to migrate an old C++Builder 2010 project to C++Builder 12
Update 1, legally using the Community Edition.
Unfortunately I have a lot of problems. The old projects compiles on
my old Windows 7 PC (yep!) without any errors. I suspect that the new
compilers are less tolerant.
My question: Which compiler versions (for C++Builder AND Delphi, Delphi
because I use a lot of 3rd-party components) can I use/select. And where
in the settings? Especially the "old" ones!

 

Any hints are highly appreciated!
BuilderFox