Answer:
I am the greatest teacher out of them all, but alas in the end I kill my pupils.
My tongue hangs out as I run over fields and streets all day. I get tied up every morning and untied at night.
I have one, you have one. If you remove the first letter, a bit remains. If you remove the second, bit still remains. If you remove the third, it still remains.
What is yellow, looks like the moon and has seeds?
What has 3 feet but cannot walk?
They are many and one, they wave and they drum, Used to cover a state, they go with you everywhere.