Answer:
As a stone inside a tree, I’ll help your words outlive thee. But if you push me as I stand, the more I move the less I am.
Tool of thief, toy of queen. Always used to be unseen. Sign of joy, sign of sorrow. Giving all likeness borrowed.
I have a ring but no fingers. I used to stay still all the time but nowadays I follow you around.
What two keys cannot open any door?
I can be swallowed, but I can also swallow you. What am I?
No matter how little or how much you use me, you change me every month.