What Am I Riddles

What am I? (medium)

Question: What is often picked but seldom chosen, never walks but can run when frozen?

Question: I have no wings but I fly,
I have no teeth but I bite.

What am I?

Question: The more of me you have, the longer your life.
The more of me you have, the less you have left.

What am I?

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

What am I?

Pain and Fear (medium)

Question: I am pain, I am fear, I will take what you hold dear, Nations shudder when I'm near, Many die when I'm here. What am I?