Is it against TOS to create a game that has lootboxes with random skins, then creating an exchange/marketplace where players can create sell orders using gamepasses, & when another player buys the gamepass in the game the item is transferred?
no I dont think, there is a question in teh questionnaire (required to publish ur game) abt it
In some countries your game will be unavailable, it will have a 13+ label in general for the rest of the world too IIRC . You also have to put a % chance of what each item has to be won.