Hi and welcome to the Delphi community!
I don't have much time right now so I'll make it quick (hope it's still enough info for ya):
1) Delphi is now object oriented, supports overloading, etc.
There's quite a lot of new stuff but if you know some Pascal, you'll still feel right at home.
2) Free Pascal can compile Delphi-style code, so it's quite compatible.
3) Yes, you can make 3d games and modellers with it. I don't know if there are any Direct3d header translations that are compatible with Free Pascal, but I'm pretty sure there are OpenGL headers for it.
Gotta go
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