What kinds of items can I use with a Reset Stone in Alchemy? Can the stones be used to de-volve any kind of item, or only special ones?
Reset Stones are only used to reset a failed Alchemiracle attempt.
Alchemiracles are special patterns involving the rare armor from Grotto end-bosses, orbs from the Legacy Bosses, and Agates of Evolution. They follow a pattern of Level 1 Item -> Level 2 Item -> Attempted Alchemiracle. Each Alchemiracle has a chance of success - the average is 20% - and a failed Alchemiracle gives you a "level 3 item", one that's not quite as good as the Alchemiracle result (a "level 4 item"), but still better than your level 2 one.
Reset stones can be used on this Level 3 result to reset it back to its level 1 state in order to attempt to succeed on the Alchemiracle again.
Bear in mind that if you are going for 100% Alchenomicon completion, you will have to perform both the failed Alchemiracle (Sapient Sandals), the successful Alchemiracle (Sentient Sandals), AND the reversion pattern (Sensible Sandals).