Does 青少年 strictly mean adolescent/teen or does it mean youth overall?
For example this sentence:
『乱れてるぞ青少年
young man has been said in English so would this only be said to a teen or could it be said by a middle aged person to a young adult man whose 20?
When do we use each and why?
I read this too: I read this here and is this correct:
せい‐しょうねん〔‐セウネン〕【青少年】ふつう、12歳から25歳くらいまでの男女のこと。
That’s from the dictionary, right? There’s no reason to doubt it would be correct.
The dictionary also says 少年 is used for boys ages 7ish to 16ish.
青年 covers a range more like 10-20.
However, I think it feels a bit old-fashioned to refer to individual people that way, even if it’s possible. I think most people are more familiar with stuff like 少年漫画 where it identifies the target audience.
I wouldn’t worry about trying to use them early on as a learner.
EDIT: I just noticed the account name… Bowing out now. These aren’t rules. No one can say how old a given character is from them.