Dogs

Yes. Dogs is free to play on Steam, so there is nothing to buy to start playing.

The minimum requirements for Dogs are: Windows 7, 64 MB RAM, 50 MB storage. It runs on Windows only. The recommended specs are in the System requirements section.

No. Dogs is a single-player game.

Yes. Valve rates Dogs as Verified on the Steam Deck: it runs well out of the box.

Yes. Dogs is the full base game. You need nothing else to play it.