Have horses won without jockey

Answer 1

A horse cannot win without a jockey on it's back as it crosses the finish line.

I think officially they have to remain mounted until they get back to the enclosure where they must be weighed again (including tack) after each race. They are also supposed to stand in the irons as they cross the finish line. If you watch a race you will see the jockeys up in the stirrups for the last few strides before the finish line.