What Am I Riddles

Question: I am a digit, but two of the ten.
Two of me make a promise.

What am I?

Question: When you fall in me your as happy as could be, but you fall into depression when you lose me.

What am I?

Question: Change a long pause into a short one by doubling a letter.What are the words?

Question: Every dawn begins with me At dusk I'll be the first you see And daybreak wouldn't come without What midday centers all about Daisies grow from me I'm told And when I come I end all cold But in the sun I won't be found Yet still each day I'll be around What am I?

Question: I have four wings, but cannot fly.
I never laugh and never cry;
On the same spot I'm always found, toiling away with a little sound.

What am I?