Why was there a general breakdown in political order between 8th and 3rd century
b. c.e.?

There was a time in the 8th century B.C.E. when the Zhou Dynasty’s ability to control its vassals broke down internal conflicts made China vulnerable to invaders outside their lands. It was also in the 8th and 3rd centuries B.C.E. when nomadic people made some drastic moves by raiding farming areas of the North China plain. There were others who settled and taken some captured existing states. There were also rivalries between lands, signals of resistance, revolts, conflicts, war and invasion. Despite all of these, there were also actions made for the intention of the consolidation of Chinese civilization which resulted to a distinct Chinese culture and identity which emerged and carried the Chinese people through the difficult times. 

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.