Difficult simple riddles for teens with simple answers

A natural state, I'm sought by all. Go without me and you shall fall. You do me when you spend, and use me when you need to eat to no end.

What always sleeps with his shoes on?

What has a foot on each side and one in the middle?

I have more than 80 keys, but I cannot open any lock. What Am I?

I get whiter the dirtier I get. What am I?

What letter is next in this sequence? M, A, M, J, J, A, S, O,__

Whoever makes it, tells it not. Whoever takes it, knows it not. Whoever knows it, wants it not.

I am something to make you think, I am something to make you know. I am something to which the answer you might never know. What am I?

It's red, blue, purple and green. No one can reach it, not even the queen.

When you have me more, you can see only less. What Am I?