This "as a teenager" has the meaning of "When he was a teenager". Then how do you say "as the title or qualification of a teenager"? Same thing?
73) You may be surprised to learn that one of the most remarkable early ballet dancers was Louis XIV of France....In 1653, as a teenager, he appeared in Le Ballet de la Nuit....
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.
99 adults participated in the marathon. The 11-year-old boy participated as a teenager.
Do you think this equation works?
The 11-year-old boy participated "as a teenager." =? The 11-year-old boy participated "when he is a teenager."
Why can't you interprete this as the example I gave you in the same way? Do you see my confusion?
....In 1653, as a teenager, he appeared in Le Ballet de la
'The 11-year-old boy participated as a teenager.' This could mean that the boy who was eleven at the time we are talking about participated later, when he was a teenager.
'99 adults participated in the marathon. The 11-year-old boy participated as a teenager.' This almost certainly means that the eleven-year-old partcipated in the teenager class/category.
As I have said before, a combination of context, co-text and common sense usually makes apparently ambiguous meaning clear.
If the eleven-year-old competed in a class only open to teenagers then he either lied about his age or he isn't eleven.
If the eleven-year-old competed in the teenage class with the competition's permission then I wouldn't say he competed "as a teenager".
The original example "In 1653, as a teenager ..." means he actually was a teenager. You can't put "as a teenager" into any sentence and make it mean that the person was viewed as a teenager but wasn't one.