Tweety Bird lives within me, Your lungs couldn't live without me. Shark divers often use me, Prisoners can't refuse me.

What do you call an alligator in a vest?

My name begins with the absolute last letter of the alphabet, but ends with the very first. No need to ponder, because I am famous enough to get a crossing named after me. What am I?

If you like this font, then the answer should be clear. I'm what jumps over the dog, quickly as I hear.

I need no crown to rule the sky, my piercing gaze sees far and wide.