Answer:
I'm tall when I'm young and I'm short when I'm old. What am I?
What is the difference between a poorly dressed man on a bike, and a well-dressed man on a unicycle?
I come without being fetched at night, hide away as soon as daylight strikes. Although I may look small, I am much mightier than what you can imagine. What am I?
I have three heads. Cut off one I become stronger. Cut off two I become ten.
I'm a god a planet and a measurer of heat. Who am I?
No matter how little or how much you use me, you change me every month.