Answer:
A king wears one on his head.
No matter how little or how much you use me, you change me every month. What am I?
These are believed to be found at the end of rainbows
I'm a starchy plant tuber that is one of the most important food crops, cooked and eaten fried, such as french fries.
What comes down but never back goes up?
A doctor might remove one from the neck of a Dracula victim.