Why does bleeding stop by rubbing moist alum?

The burning sensation of bee sting can be stopped by rubbing the affected are a with sopa this is because

While learning to ride a bicycle Boojho lost his balance and fell. He got bruises on his knees and it started bleeding. However, the bleeding stopped after some time. (a) Why did the bleeding stop? (b) What would be the colour of the wounded area and why?

A match stick can be lighted by rubbing it against a rough surface. Why ?

It is difficult to stop bleeding from a cut in human body at high altitude. Why?

Why does sound travel faster in moist air than in dry air ?

Someone's finger gets cut accidentally while chopping vegetables and starts bleeding. The bleeding stops after a few minutes. What are the steps that lead to stoppage of bleeding?

Why does a plastic comb rubbed with dry hair attaract tiny pieces of paper ?