Reversal of Fortune

You can’t cast the copy if an effect prevents you from casting instants or sorceries, or from casting that particular instant or sorcery. It doesn’t matter whether your opponent can cast the card at this time; the only thing that matters is whether you can cast it.

Reversal of Fortune creates a copy of the card in the other player’s hand, then allows you to cast the copy from that player’s hand without paying its mana cost.

If you don’t want to cast the copy, you can choose not to; the copy ceases to exist the next time state-based actions are checked.

The spell is cast from your opponent’s hand, not yours, which can be important for some cards.

If the copied card is a split card, you may choose to cast either side of the split card but not both.