If so, you can cast the card as the adventure or as the creature. If you cast it as the creature, then everything is as normal. If you cast it as the adventure, then it will be an instant/sorcery on the stack and resolve as such. As part of the resolution, the card goes to exile, and you can henthforth cast the creature from exile so long as it remains there as per the usual rules for casting the creature. (If the card has flash, you can cast it with instant timing, otherwise it's the usual sorcery timing.) You can only cast the creature from exile if it went there through its adventure. Casting the creature is another spell, and can be responded to and countered as such.
When I cast the creature as an instant, It goes into exile,
Can I now pay the mana cost of the creature to bring it onto the battlefield?
If so, you can cast the card as the adventure or as the creature. If you cast it as the creature, then everything is as normal. If you cast it as the adventure, then it will be an instant/sorcery on the stack and resolve as such. As part of the resolution, the card goes to exile, and you can henthforth cast the creature from exile so long as it remains there as per the usual rules for casting the creature. (If the card has flash, you can cast it with instant timing, otherwise it's the usual sorcery timing.) You can only cast the creature from exile if it went there through its adventure. Casting the creature is another spell, and can be responded to and countered as such.
Former Rules Advisor
"Everything's better with pirates." - Lodge
(The Gamers: Dorkness Rising)
"Any sufficiently analyzed magic is indistinguishable from science."
(Girl Genius - Fairy Tale Theater Break - Cinderella, end of volume 8)