Answer:
I am the greatest teacher out of them all, but alas in the end I kill my pupils.
He has married many women, but has never been married. Who is he?
A precious stone, as clear as diamond. Seek it out whilst the sun's near the horizon. Though you can walk on water with its power, Try to keep it, and it'll vanish within an hour.
My first is in fish but no in snail. My second is in rabbit but no in tail. My third is in up but not in down. My fourth is in tiara but not in crown. My fifth is in tree you plainly see. My whole a food for you and me.
Some try to hide, some try to cheat. But time will show, we always will meet. Try as you might, to guess my name. I promise you'll know, when you I do claim.
They are many and one, they wave and they drum, Used to cover a state, they go with you everywhere.