No.
No. Steam games run on PC/mac and not on Sony PS4 (or nintendo or xbox) at all.
Yes the newest war-games need steam because to play online they must have a network where u can chat and play. PS3 have PS network, Xbox have xbox live but we have steam!
yes here are some [the orange box] [left4dead] [left4dead2]
Yes, you can.
The games are available and are very inexpensive when compared with the Xbox 360 games
You would haft to transfer the games to your Xbox 1 in order to.
You have Fable 1 GTA SA Halo 1
You cannot.
Steam is the best site for PC games. Google "Steam" and download their client. It has the most reliable source of games. I have yet to find 1 glitch in a a steam game.
Xbox 360 is fully compatible with Xbox 1 - x360 has inside emulator of xbox1. I played several original xbox1 games on my 360.
Rust is not available for the xbox 360.