Your game can be in another language. But it's recommended to have an English version as well so we can double check it fits the yaoi Jam rules.
Can you clarify what you mean by not people?
Hi ChekushTwist
So that's a tough one. Since itchio updated their rules on games that contain adult content some time ago to prohibit a bunch of stuff, one of which includes bestiality and animal-related content, it would really depend on what kind of game you end up making. And if you want to make it NSFW or commercial then that would probably get it banned from itchio and the jam.