Answer:
I am a box which holds keys but not locks. With the right combination, I may unlock your soul. What am I?
I make billions of dollars selling windows. Who am I?
When you buy me I am costly, but the only use I have is hanging only. What am I?
You can see me in water, but I never get wet. What am I?
What kind of table can you eat?
No matter how little or how much you use me, you change me every month.