If the only reason you didn't behave that way to begin with is that you lack the money and power to evade the consequences, then yes. You really are that person.

Yes. "Power doesn't corrupt, it reveals"

I believe the original statement is an oversimplification. What actually happens is that extreme situations, both positive and negative, can help you discover things about you that you didn't know before.

Apart from that, the problem with "who you really are" is that individual is more of a process than a static thing, so any such reification becomes invalid in the next instant.

Spot on