Reverberate

If the copy says that it affects "you," it affects the controller of the copy, not the controller of the original spell. Similarly, if the copy says that it affects an "opponent," it affects an opponent of the copy's controller, not an opponent of the original spell's controller.

If the spell Reverberate copies is modal (that is, it says "Choose one —" or the like), the copy will have the same mode. You can't choose a different one.

You can't choose to pay any additional costs for the copy. However, effects based on any additional costs that were paid for the original spell are copied as though those same costs were paid for the copy too. For example, if a player sacrifices a 3/3 creature to cast Fling, and you copy it with Reverberate, the copy of Fling will also deal 3 damage to its target.