Lock next slide

Hi
I wanted to know if there was a way to lock slides for a certain amount of time and unlock them one after the other. Let me explain: I have a video-only course and I would like the student to be obliged to see unit 1 and then unit 2 without being able to jump to unit 2. is it possible? Also since the videos can be as long as 40 minutes I would like to know if there was a mechanism for saving progress. I know it is complicated but I would like to have some ideas to work on it

Thanks