If you want to ask about a certain objective, or what do you have to do to pass a stage in a video game, is this allowed on Arqade? If so, which tag do you use for the question when it isn't one of the best known games and there isn't a tag?
It is perfectly fine to ask about any (game-related) problem you encounter when playing a game.
As a heads-up, asking about tasks that are solved using simple or obvious solutions, or solutions that can easily be found online, might get you some downvotes - reversely, harder, well-known, or obscure solutions, or ones that hard to find online, might get you more upvotes. We expect users to have done some research before asking questions here.
As for the tags you use, as long as you cannot create them yourself, a user with higher reputation will edit it in.
You don't have to use a specific tag for the nature of the problem you're facing, though. If they exist and are necessary or helpful, you can edit them in later, or someone else might do so.