The last question of the last node, is that even solvable within the timelimit?
Also is there only one ending?
Viewing post in [18+] Succubus Tales - Unmonitored Desires comments
I'm not sure which you might be referring to, do you mean the ending linked with screenshots on the page or by how they're listed in game? I'll assume game and drop more detail on that order.
END 1 (ANNA) - Can be achieved by succeeding on all of the puzzles and agreeing with Anna.
END 2 (BEL) - Can be achieved by having a mix of both success/failure of the puzzles, you could get all of the puzzles correct but if you are dismissive to Anna you can get this ending or vice versa.
END 3 (RICHARD) - Can be achieved by failing all the puzzles and being dismissive towards Anna