First, I would have liked some options that would allow you to turn down the music volume, but I understand that you don't have that much time for these fancy features in a game jam game.
I like how you start with actual levels that make up the tutorial. As a player, you don't want to feel handheld when you start the game.
But then the game is so short. The mechanic is cool, and I think you could have made some cool puzzles with it, but you never really get there. Some levels had some cool ideas, but you basically could solve every level by just walking to the position of the key and rewinding.
That's kinda sad, as I think there's a lot of potential in your idea. I think what the game lacked the most where other game elements, maybe some doors and pressure plates? There are only so many things you can do with blocks and spikes.
If you want to learn more about puzzle design, I would recommend checking out the playlist by Game Maker's Toolkit. I found them very helpful when designing puzzles for our game.
Nonetheless, I think you did a good job as we only had a week and you were making everything except the music.