- As long as it isn't under contract anywhere and doesn't violate the minimum guidelines, you can post it on Tapas. And posting to Tapas doesn't automatically put you under contract.
2-3. Their policy, under Content and Community Guidelines ( https://help.tapas.io/hc/en-us/articles/115005323707-Content-and-Community-Guidelines ) is no, you can't use AI anything. Because of its possibility of accidentally infringing on copyright. That said, as long as you're not trying to sell it at all, if you do an image search to make sure you're pictures don't exist (or copy) an existing picture, if you repurpose/edit those pictures be more 'yours', and if you're not claiming credit, then it's highly unlikely that they'll check into it.
If you want a platform that allows ai art (especially if you're doing the above for copyright purposes), reamstories.com allows it. It's a subscription/publishing platform specifically for authors. It's just a little clunky right now for pictures, though not impossible (I've experimented
).