Answer:
Add a T and I shoot through the sky. Then add an S and I multiply. What word is it?
Take one out and scratch my head I am now black but once was red.
What surrounds the world, yet dwells within a thimble?
Two little holes in the side of a hill. Just as you come to the cherry-red mill.
In Paris but not in France, the thinnest of its siblings.
You use it between your head and your toes, the more it works the thinner it grows.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?