What Am I Riddles

Question: You wear me every day but you never put me on.
I will change colors if you leave me out too long.

What am I?

Question: What gets longer when pulled,fits between breasts, slides neatly into a hole,has choked people when used improperly,and works best when jerked?

Question: You find me behind the stars; or in a sixth, seventh, or third.
It takes something round, a computer, and me to make pie.
I am bigger than anything you can think of.

What am I?

Question: I'm tall when I'm young and I'm short when I'm old.What am I?

Question: After you go through a fall I will take over.All life will stall, or at least grow slower.What am I?