How about an answer for an answer? I'm stuck on 17 scenes as well but it's a different one.
Yeah, for the 18th scene you need to beat the novice level of the dodgeball without being hit once. Took me a while but it was pretty fun and the scene is quite nice.
Your turn, how the hell do I get the 5th one (between the priestess orgy one and the otters in the river one), I've been looking for over an hour-
I also haven't found a use for the jar unfortunately, maybe it's just there to fill up the store for now?