Rewind | Magic: The Gathering
Formats Rewind is Legal in
Official Oracle Text for Rewind
Official Rulings for Rewind
7/1/2012 : When Rewind resolves, you choose up to four lands and those lands untap once. You can't choose one land and have it untap four times, for example.
7/1/2012 : If the spell is an illegal target when Rewind tries to resolve, perhaps because it was countered by another spell or ability, Rewind will be countered and none of its effects will happen. You won't untap any lands.
7/1/2012 : If Rewind resolves but the target spell can't be countered, you'll still untap lands.