Which historical event marks the beginning of the middle byzantine period?

Empress Theodora’s reinstatement of the venerations of icons was the historical even that marks the start of the middle byzantine period.  Empress Theodora was known as the most influential and most powerful among the Byzantine empresses and is known in the modern times as the saint of Eastern Orthodox Church.  After the success of the Nika revolt, which was a way of Theodora to prove herself to be a worthy leader,  she and Justinian,  her husband rebuilt and reformed Constantinople and made it as the most splendid city the world has seen for centuries. The term “byzantine” even refers to the art and architecture of Constantinople and its surrounding reigns.

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.