Forcing quiz takers to select a response

I am setting up a quiz with multiple slides (currently individual slides, rather than a question bank). I display results for all questions at the end of the quiz. I have added conditions to each question such that, if the user does not select a response, then an "OOPS" layer is revealed which says, "You must select a response!".  When the user clicks "Continue", that layer is hidden.  When the user  selects a response, the quiz moves on to the next page. Results are tabulated correctly and all works well.... UNTIL the user presses the "Review" button, and then the "OOPS" layer appears on every review page. (OOPS layers are set to "Hide this layer when the user clicks" (on the "Continue" button).  I have tried adding "Hide this layer when timeline ends" but no luck.  Any suggestions? (or am I dreaming  the impossible dream?!)  

Also, is it possible to review ONLY the questions that were not answered correctly?

Thank you!

Debbie