Hi, my sim had a cc hair but after birthday it changed into ponytail... (which is only for females..) it's any way to keep cc hair without editing them after birthday? (i mean some townies are using cc hair and they are losing them :/ )

Uhm, change it back? It's normal that sims look different after they get older!

I swear that sims used to keep their hairstyle after aging up if the style was available for their age group. Something changed because some players are having a heck of a time with the changing hairs (me included). The more time we have to spend in CAS the less time we have to play, and it's a royal PITA.

What, you don't like the base game pigtails? D: lol that's the hair I see a lot of people get stuck with.
Anyhoo, have you checked out the Dresser mod at NRaas? I could be wrong, but I thought there's an option in that mod about age-up hair.

change back about 40 sims... and then about 6 sim days later change it again? it's useless (i mean for example, young adult changing to adult with no cc remain his hair.. but with cc hair he changes it to another...)

Sorry but male with basegame pigtails? no... but thanks for advice to use Nraas Dresser