groet

Because they are the player that can do something about the Fall damage. Could also be a sorcerer or wizard.

I think its not about reversing the direction of inertia but more of a "you keep your speed when activating/deactivating the belt, just in the other direction". You can't use it to cancel fall damage by reversing gravity for 0.1sec before touching the ground because you also reverse your falling speed when you reverse gravity.

Mammals mostly don't live that long and reptiles aren't the most cuddely. But sloths or primates can live to 50 years. And some birds can outlive you easily with cockatoos getting to 120 years occasionally