Lefty Gunz
Superstar
I don't think she will bruh. Unless they do a time skip in the flashbacks, cuz Gillian was probably not even born by then. Nucky was already sheriff when he introduced them I'm pretty sure.
She will.
They're not just flashing back to when Nucky was a kid, soon they'll show flashback to when Nucky was in his 20s and sheriff, according to Winter
According to wikipedia, somebody named Marc Pickering is playing 20 year old Nucky