Answer:
I am used when you jump off a bridge for fun.
I come with a train and go with a train and the train doesn't need me but can't go without me.
I am a seed with three letters in my name. Take away the last two and I still sound the same.
He has married many women, but has never been married. Who is he?
I turn everything around but I cannot move. When you see me you see you!
It flows out of the soil, It burns you if it boils, And holds us in its coils, More valuable than gold, As black as it is old.