Could the French Revolution have been prevented? why or why not? if so at what point?

In theory yes, it could've been avoided, if the monarchy was willing to give up some power, but in reality no, it couldn't, because the idea of a constitutional monarchy couldn't possibly survive in a deeply absolutist world.

depends on the age of the teen, many believe by the age of 16 a person should know the strong difference between right and wrong along with the difference between risky and immediate death. swimming with sharks might be dangerous but swimming with sharks while bloody meat is attached to you is just insane. even more if you have no idea what you're doing. however, no matter the age, as long as the person is skilled enough and has the mental and physical capacity to control their actions doing whatever sport they put their mind to is all that matters.