If the spell requires any targets, those targets are chosen when the spell is finally cast, not when it's exiled
Besides that, your best bet is to prevent the accumulation of the counters in the first place with a Solemnity
Eldrazi are one of the most popular creature types in Magic, so there's always going to be some kind of value to them
Any time you have priority, you may turn the face-down creature face up by revealing what its disguise cost is and paying that cost
In Strixhaven: School of Mages, the set contained 63 different Mystical Archive cards in the respective treatments
Original Dual Lands The best fixing lands ever printed, and part of the reason so many players get priced out of Legacy and other older formats, the original dual cycle includes strictly better basics in cards like Volcanic Island and Scrubland