Hi, i previously assumed i was going to ceiling mount my projector. Well now the idea came into my head that i couldnt because my loft builder has put on plasterboard or drywall in the US, about 2cm thick, can i still?

It depends.
How is that board mounted and what is behind it?

Most often we use long screws that pass trough the plaster board into something more substantial.

just with normal screws on the corners and there is nothing behind it, so can i like, nail a thick peice of wood onto it and put the projector on that?

PS you have the coolest ht ever! when do think its going to get finished??

Well now the idea came into my head that i couldnt because my loft builder has put on plasterboard or drywall in the US, about 2cm thick, can i still?

What is this plasterboard or drywall mounted to?

old joists that were just there on the roof