Don’t rely on mods, multiversus have disabled them after it released.

Very much depends ob the game. Online games? Most likely not. Offline games like No Mans Sky or Sims? Sure, that is possible.

I dont know about battlepass but the skins are possible with mods, but are only visible to you, not to other players.

If you’re talking about online multiplayer games, they’re server sided so no. Though, for some games, there are people who will sell you battle pass codes for cheaper because they buy them in countries with a weak currency, it all depends on the game.