What Am I Riddles

Question: I have two rings. I move by request. If the mixture isn't right I just sit and rest.

What am I?

Question: What is as big as you are and yet does not weigh anything?

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

Question: You struggle to regain me.
When I'm lost, you struggle to obtain me.
I pass no matter your will,
but I'm your slave to kill.
What am I?

Question: A five lettered word, I'm used to make bread.
Remove one letter and I'll burn you instead.
Remove two and do this to your stew.
Mix that around and a good drink we will brew.