What kind of key can't fit in a lock but can turn a handle without any doubt

I am both male and woman, I live where most living things couldn't, I always frown though my name suggest I shouldn't, What am I?

A cannonball causes a large one A jack knife a little less so A rip entry, hardly none But a belly flop? Look out below!

I have no lungs but I am alive. I need water to survive. I'm up and about night and day, I go with the flow, you might say.

Rhythmic spasms in a throat symphony, interrupting silence like a rogue conductor; cured by fright or holding breath.