Hi! Sorry it took me a bit to get back to you. To answer your questions:
This is a supplement to a game called Troika! You won't be able to use only it to play, but a free SRD is available on Itch. Although I suggest getting the full game, it's pretty awesome.
I'd say Troika supports up to 6-7 players, including a GM. There's no solo mode for it, and the average play time would be around 3 hours. At least that's how long I'd be willing to play a single session.