multiple

I was looking through motogp champions list and saw some riders like the legend agostini had raced in more than one category. so my question is are current modern era riders are allowed to compete in multiple categories? if not why?

Looking at the video, it is clear that Rossi was hit by Marquez multiple times. Why is this not brought to attention? Also looking at the video it is clear that Rossi's foot coming off the peg was only a reflex reaction, after Marquez first hit Rossi. Why is this nit brought to attention...