Answer:
I only exist when you are here. Where you never were I can never be.
Lives in winter, dies in summer, and grows with its roots upward. What is it?
I know a word of letters three. Add two and fewer there will be. What is the word?
What begins with T ends with T and has T in it?
Angels and pilots work with me.
No matter how little or how much you use me, you change me every month.