The sheets presumed to be printed later (a Shadowless-exclusive holos sheet as well as commons, uncommons and Basic Energies sheets matching those used for Unlimited) are highlighted in grey
As long as this card is face-up on your side of the field your opponent can't add cards from their graveyard to their hand
But you need to consider many factors, such as the condition, rarity, and uniqueness of the card
However, if you do choose a target, and that target is illegal at the time the spell tries to resolve, the spell won't resolve and none of its effects will happen
the casting cost is used when you play it from your hand, and the harmonize cost is used when you play it form the graveyard
Still, it's funny to mock it, and that won't change any time soon