What Am I Riddles

Question: What goes up and down the stairs without moving?

Question: No matter how hard you try,
I can open what you can't.
If it wasn't for me,
on your front porch you would stand.

What am I?

Question: Everyone has me but nobody can lose me.What am I?

Question: Drop me and the world will shatter,
and you can always find me where you empty your bladder.

What am I?

Question: I have roots that nobody sees,
I'm taller than any trees,
up and up I go,
but I never grow?

What am I?