Answer:
Add a T and I shoot through the sky. Then add an S and I multiply. What word is it?
Two horses, swiftest traveling, harnessed in a pair, and grazing ever in places. Distant from them.
I'm a type of pizza that is folded in half before cooking to contain a filling
It's in your hand though you can not feel it. Only you and time can reveal it.
Everyone has it and no one can lose it, what is it?
Break me and I am better immediately set and harder to be broken again.