3) Pretty sure they can. Last year had a FA from 2015 graduation I or something class working D1 on a MSP-AMS flight telling me she was really new.
Other D1 aisle on that flight was also worked by a new FA (she was originally on stand-by)
Noticed that if there are FA's that are really new the pre-flight safety demonstrations are a live briefing performed by those flight attendants standing up in the aisles. Don't know what's up with that, the more senior mama's never seem to do those live briefings on TATL flights.