30+ levels is a big commitment in a game jam with 2k submissions as most people will play your game for a few minutes, you can see from this thread how long its taking me to go through everyone when I give 10-15 minutes at a time so I definitely think you should introduce things earlier on. The mechanic is simple enough that most people should grasp it right away and the introduction of an additional rewind doesn't change the core idea of the game so I don't think players need time to adjust to how they play the game again.
That's just one mans opinion though.