You can’t cast a plotted card on the same turn it became plotted. On any future turn, you may cast that card from exile without paying its mana cost during your main phase while the stack is empty.

If a card with no mana cost gains flashback equal to its mana cost, it has no flashback cost. It can’t be cast this way.

To determine the total cost of a spell, start with the mana cost or alternative cost (such as a flashback 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.

“Flashback [cost]” means “You may cast this card from your graveyard by paying [cost] rather than paying its mana cost” and “If the flashback cost was paid, exile this card instead of putting it anywhere else any time it would leave the stack.”

If a card has multiple instances of flashback, you may choose any of its flashback costs to pay.

A spell cast using flashback will always be exiled afterward, whether it resolves, is countered, or leaves the stack in some other way.

If you cast an instant or sorcery with in its mana cost and a flashback cost equal to its mana cost, you still choose the value of X as part of casting the spell and paying that cost.

If you’re casting a plotted card from exile without paying its mana cost, you can’t choose to cast it for any other alternative costs. You can, however, pay additional costs, such as kicker costs. If the plotted card has any mandatory additional costs, those must still be paid to cast the spell.

If a plotted card has in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

Exiling a card using its plot ability is a special action. Once you announce you’re taking that action, no other player can respond by trying to remove that card from your hand.

If you cast a spell with flashback, you can’t pay any alternative costs such as overload costs. You can pay additional costs such as kicker costs. If the spell has any mandatory additional costs, you must pay those to cast the spell with flashback.

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 flashback only when you could normally cast a sorcery.

Plot abilities are written “Plot [cost],” which means “Any time you have priority during your main phase while the stack is empty, you may pay [cost] and exile this card from your hand. It becomes plotted.”

You can cast a spell using flashback even if it was somehow put into your graveyard without having been cast.