If an effect allows you to pay an alternative cost rather than a spell's mana cost, you may pay that alternative cost when you jump-start a spell. You'll still discard a card as an additional cost to cast it.

When casting a spell with jump-start, 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 jump-start only when you could normally cast a sorcery.

A spell cast using jump-start will always be exiled afterward, whether it resolves, it's countered, or it leaves the stack in some other way.