Only if you have an already existing condition that it would be wise to talk it over with your doctor. Not if you are a normal, active and healthy human being.

No, it's not required, but as with starting any other physical activity, it's not a bad idea.

Nope, but it'll come handy when you or others are in serious injury! :D

no you dont, if you have some preexisting condition you should notify the instructor about it.