Answer:
I am always around you but often forgotten. I am pure and clean most of the time, but occasionally rotten. What am I?
Sing me to a baby about to go to sleep.
I widen my jaws when you poke two fingers in me. I especially like to devour papers
I have all the knowledge you have. But I am so small that I can fit into your hands. What am I?
What kind of coat can only be put on when wet?
No matter how little or how much you use me, you change me every month.