The "show answer" button should be coming soonish (maybe 3 months?). I think it's the next big feature that I tackle.
I'm also very interested in fixing flaws in the puzzles. For some reactions I made up mechanisms based on my own intuition because they weren't very well described in my source materials. If you're willing, could you let me know which mechanism(s) or puzzle number(s) need fixing, what you think the mechanism should be, and ideally a source that shows the correct mechanism? I would very much appreciate this type of feedback; it's important to me that the puzzles reflect real chemistry!