Trouble with Variables and States

Before I duplicate a scene (English) to add 11 languages, I want to get this right! Course is 6 videos, each followed by a review slide with hidden icons and text.

Problem 1: When a user clicks an icon, the corresponding text and the next icon appear. The Next button is hidden until the last icon is clicked and the variable is NextButton = False. Clicking the last icon changes the variable to True. I would like user to be able to go back to the full review slides without having to click through all the icons and for the Next button to be there, so I added When timeline starts -> Change State of X to Normal if the NextButton is True. Works for one slide but none of the others. Cannot see why not!

Problem 2: I want to hide/disable the Next button on the videos until they are watched at least once. I've attached a picture of the triggers for each video. Works for the 1st, but not the rest. It's probably too complicated, but I was troubleshooting and now don't recall what made the first one work! Help!