BoomXR

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

The minimum requirements for BoomXR are: Windows 10, GeForce GTX 970, Intel Core i5-4590, 4 GB RAM, 100 MB storage. It runs on Windows only. The recommended specs are in the System requirements section.

No. BoomXR is a single-player game.

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