Fan games are allowed, but if you’re going to use any assets or try to monetize off of them (premium payouts don’t count because there’s no real way to stop that) try to contact the creator of the original game and ask them if you can. If you can’t contact them or they don’t allow you to just don’t do the previously mentioned stuff.
Sorry for the late response.
Your own gamepasses? Unless you got consent from the original game owner, no.
What you can do is if the player bought a gamepass FROM the original game, the gamepass would also benefit the player in your game. This is allowed as the monetization would still be going towards the original game owner and you’ll also be able to use gamepasses (although you probably should make a disclaimer that the gamepasses aren’t yours and in fact go 100% to the original developers) .
I don’t know if I explained this properly but an example of this is with Robot 64 Mods