What Am I Riddles

Question: We have what we did not find; what we did find we left behind.

[What do we have?]

Question: Of the king I am blue and of the peasant I am red.Of the frog I am cold and of the dog I am hot instead.What am I?

Question: My first two are male, and my first three female.
My first four save them both, and my whole is a female of the same sort.

What am I?

Question: If you're looking for something sweet I know what to do.
But if you don't like heat I'm not for you.

What am I?

Question: Not chest or box is now discussed. Money can be held in it, but just as we test its metal, within it there is rust.

[What is it?]