The player has seen all of Rise of the TMNT and the movie and can play Donnie from either the end of season 2 or the end of the movie. Depending on canon point he'd be 14/15 (End of series) or 16 (movie). I mostly play him end of movie though.
EDIT: Having read the 40th anniversary comic, the Rise one, "Farewell" and it apparently takes place in 2024 which if played from would make Donnie 20 but I have no concrete proof of this timeline and the characters don't look older? I'm currently refraining from playing from it on memes.
Canon Point for memes
EDIT: Having read the 40th anniversary comic, the Rise one, "Farewell" and it apparently takes place in 2024 which if played from would make Donnie 20 but I have no concrete proof of this timeline and the characters don't look older? I'm currently refraining from playing from it on memes.