Unlike the other two cards with this style of ability (Arcane Savant and Caller of the Untamed), if you have more than one Volatile Chimera in your deck, you need only reveal one of them because you can exile as many creature cards that aren't in your deck as you want, with a minimum of three. If you do reveal more than one Volatile Chimera before shuffling, you'll have to exile at least three creature cards for each of them.

The copy effect created by the activated ability doesn't have a duration. It will last until Volatile Chimera leaves the battlefield or another copy effect overwrites it.

No enters-the-battlefield abilities of the creature card Volatile Chimera is copying will trigger. Volatile Chimera was already on the battlefield.

After Volatile Chimera copies a creature card, that card remains in the pool of cards you can choose with the last ability.