Short answers, pulled from the story.
The average age of onset for puberty is 10 to 11 years for girls and 11 to 12 years for boys. This biological process triggers a surge in hormone production that initiates a chain reaction throughout the body.
Spermarche occurs on average at age 13 for males. It serves as the major landmark of puberty for boys while facial hair typically appears between 14 and 17 years of age.
Girls usually reach full physical development around ages 15 to 17 while boys complete puberty around ages 16 to 17. The human brain reaches 90% of its adult size by six years of age before white matter increases linearly over the course of adolescence.
Identity achievement rarely occurs before age 18 despite self-examination beginning early. Erik Erikson argued that not everyone fully achieves identity despite having a self-concept, and James Marcia developed a method testing progress through occupation ideology and interpersonal relationships categories.
An American study from 2002 reported the average age of first sexual intercourse was 17.0 for males and 17.3 for females. A separate study conducted by YouGov for Channel 4 found twenty percent of 14 to 17-year-olds surveyed revealed first sexual experience at 13 or under in the United Kingdom.
G. Stanley Hall published Adolescence in 1904 defining it as the period from ages 14 to 24 viewing it primarily as internal turmoil and upheaval. His assertions stood relatively uncontested until the 1950s when psychologists like Erik Erikson and Anna Freud formulated their theories.