If you have a sorcery card in your graveyard with flashback do you have to still treat it as a sorcery or could you flash it back on your opponents turn or no?
Flashback only alters where you cast the spell from (in this case, your graveyard) not when you cast those spells.
So no, sorceries can only be cast on your 1st and 2nd main phases, with priority and the stack clear.