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.

“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.”

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.

To determine the total cost of a spell, start with the mana cost or alternative cost (such as a flashforward cost) you’re paying, add any cost increases, then apply any cost reductions. The mana value of the spell is determined only by its mana cost, no matter what the total cost to cast the spell was.

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.

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.

Playtest cards aren’t legal for play in any tournament format other than Mystery Booster Limited formats. On the other hand, we expect they will spice up a wide variety of non-tournament games (as long as everyone’s on the same page about using them!).

Playtest cards use a modified version of game symbols, such as {T} and {W}. These modified symbols should be treated as the standard symbols during play.

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.