On The Orange Box(Disc), or from the Xbox Live Game Marketplace as an arcade game.
Yes!
Yes. It is an Xbox 360 game.
You can't.
No, Portal 2 is also out for PS3 and PC.
No Portal 2 is for PC, Xbox 360 and PS3.
Yes. Portal 2 is on Xbox 360, PS3 and PC.
No
Yes, you can get in stores or online.
In stores and online.
ps3, xbox 360 and pc
No. Portal 2 is available on XBOX 360, PS3 and PC only.
PC, PS3, XBOX 360, Mac,
ps3, Xbox 360, PC/MAC