Supersports Driving behaviour

Hello, I hope I get a few helpful answers here. To me, I am a beginner and own a super sportsman with ABS and a few electronic things zb like rainmode, I have a few questions about this. I read and hear a lot that you should not brake with the front brake at step speed? Can anyone explain this to me more precisely? With a 600 nakedbike this was all no problem. On the Internet I find unfortunately not much. Can you with a supersport What do I have to pay attention to when it rains for braking behaviour? I was just riding nakedbike before, but I don’t think that you can compare it. Now the last question is ?? there are many rides that are stamped out of gravel and sand and therefore tight, can you ride on it without any problems? Or do you rather slip away because the tyres of an athlete don’t have a lot of grip? I am happy to receive further tips from experienced bikers.