When a spell is copied by something like Reverberate or Pyromancer Ascension it makes an exact copy, unless the effect that makes the copy allows you to make changes. Most often these effects will allow you to choose new targets, but other values will stay the same. For example, the value of X in the mana cost of a spell will be the same as in the original. Also, any modes chosen when the spell was played will be the same in the copy a in the original.