Can you make a rule to have no NSFW or make people clearly stated in the title of the game for people who don't want to see it.

I think this is a reasonable ask, but a lot of people doing game jams are 18+, and may disregard this even if it is a rule. I advise that if you are avoiding NSFW you should have a parent or trusted one by your side while inspecting others creations

i don’t think anybody cares for nsfw, as this a small jam, but also sorry, no thanks, you can do nsfw. Itch.io requires you mark it as such, so nobody would get tricked in any way. It’s fine to do it. Hope this clears that up