Ok so here's your answer:
When somebody falls off the screen they get respawned at the next checkpoint. They don't spawn until the rider in last passes through that checkpoint though, and they spawn at the same speed as the rider in last.
Falling off the screen causes you to lose a point. The maximum points you can get is 10 per race. You would get this if you come in 1st and don't fall off the screen. So if you fell off the screen and came in 1st you would get 9 points. Then the person in 2nd if they didn't fall off the screen would get 8. It's very simple.
The camera angle follows the rider in 1st. It shows everybody on the screen but advances with the rider in 1st this way you have to keep up with him if you don't want to fall off the screen.
I'm pretty sure that explains it all but of there are any more questions then feel free to ask and I will do my best to answer
