genitalia need to be fully obscured, as well as anything gentalia-like,

I had a scene when tips of this guys "hair" are wet and kissed and that needed to be removed
and if you're depicting an oral act, head of the character doing the act needs to be fully obscured as well
I've also been consoring nipples, while I wasn't notified about them by staff, some creators of comics I read were told to hide them to stay on the app (though one of them recently got told that now they're ok, but I don't know...)
Your best bet in general is to contact tapas staff and ask what needs to be changed in your series to be allowed on the app, as there are no clear, set in stone guidelines.