Boltfire

You must still follow any timing restrictions and permissions, including those based on the card’s type. For instance, you can cast a sorcery using flashforward only when you could normally cast a sorcery.

For many playtest cards, you’ll need to make a generous assumption that basic game rules would be updated to allow them to work. The Mystery Booster 2 Playtest Card Notes section (reproduced here in individual Gatherer rulings) provides guidance for fitting these cards into the existing rules structure.

A spell cast using flashforward will always be put on the bottom of its owner’s library afterward, whether it resolves, is countered, or leaves the stack in some other way.

“Flashforward [cost]” means “You may cast this card from exile by paying [cost] rather than paying its mana cost” and “If the flashforward cost was paid, put this card on the bottom of its owner’s library instead of putting it anywhere else any time it would leave the stack.”

If some other effect gives you permission to cast Boltfire from exile, such as if you exiled it with Dark-Dweller Oracle, you may cast Boltfire using either permission.

When you cast Boltfire normally, it will go to the graveyard after it finishes resolving. You’ll have to figure out how to get it into exile to cast it with its flashforward ability.