How reset the Position of all puzzle pieces?

There are a few ways to do it.

1. You can reload the scene if each puzzle is it's own scene.

2. If each puzzle is just settings and loaded into one scene that houses all puzzles, then you could just redo the loading process for that puzzle just how you would when first starting the puzzle.

3. If neither of those work, then you in Awake() or Start() for each puzzle piece you can save it's starting position. When you want it to reset, just tell each puzzle piece to return to the starting position that you saved initially.