Answer:
I am one with eight to spare, lest I lose my one. I'm not a number. What am I?
you cannot keep me until you have given me
I let water fall on you while everyone else stays dry. What am I?
rub me and a genie might appear
I am a food with 5 letters. If you remove the first letter I am a form of energy. Remove two and I'm needed to live. Scramble the last 3 and you can drink me down.
No matter how little or how much you use me, you change me every month.