What Am I Riddles

Question: Without me, nothing exists. What am I?

Question: Until I am measured, I am not known. Yet how you miss me, When I have flown What am I?

Question: Poke your fingers in my eyes and I will open wide my jaws. Linen cloth, quills, or paper, my greedy lust devours them all.

What am I?

Question: Paint me up to look real good,
Then take me to the shop to maintain under the hood.
Use a small brush to make no mistake,
Or just replace me with something fake.

What am I?

Question: Thirty white horses stand on a red hill,
First they champ,
Then they stamp,
Then they stand still.

What are they?