Knock

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

The minimum requirements for Knock are: Windows 10, Intel Pentium, 256 MB RAM, 200 MB storage. It runs on Windows only. The recommended specs are in the System requirements section.

No. Knock is a single-player game.

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

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