Ha, that's a good question
Crappy cope out answer is the "natural morphing" of metamorphosis doesn't take anything away.
Tobias's powers come back through the Ellimist, such that hawk is his natural form-thus what he had obtained while human-Dude-is lost.
The butterfly transformation let Cassie go back to her base form of human, it cause it to be something else.
I guess.
Don't know about the butterfly. I'd assume so, but then she acquired the caterpillar. I don't think there's an agreement on age of acquired item and it's effects of what you morph