20 Sept 2016
You can't cast Spark of Creativity without targeting a creature. If the creature becomes an illegal target for Spark of Creativity, none of its effects happen. You don't exile the top card of your library.
20 Sept 2016
You must pay all costs to play the exiled card. You may pay alternative or additional costs. If the card has any mandatory additional costs, you must pay those.
20 Sept 2016
Spark of Creativity doesn't change when you can play the exiled card. For example, if you exile a creature card without flash, you can cast it only during your main phase when the stack is empty.
20 Sept 2016
If a card in exile has {X} in its mana cost, X is considered to be 0.
20 Sept 2016
If a land card is exiled this way, you can play that land card until end of turn if you have any available land plays.