Jace's Mindseeker

When casting an instant or sorcery card this way, ignore timing restrictions based on the card’s type. Other timing restrictions, such as “Cast [this spell] only during combat,” must be followed.

If the five cards are put into a public zone such as exile instead of a graveyard (perhaps due to the ability of Rest in Peace), you can cast one of those instant or sorcery cards from that zone.

If you cast an instant or sorcery card this way, you do so while the ability of Jace’s Mindseeker is resolving. If you choose not to (or can’t), you won’t get a chance to cast one later.