I come at the start of rocket and at the end of cracker. What am I?

Question

I am two five letter names 500 is at the start, 10 is in my heart. In the middle of that is 1, Near the end is none. At the end is 14, Yet that is not all that has been seen. It's a word that rhymes with liver, Yes, to the left of that is river.

Answer 1

The letter R