Yes.
It usually goes like this: Level job to 18, do subjob quest, level subjob. Then level main job / subjob to 30 to get the quest(s) for the advance job you want to unlock.
Yes.
It usually goes like this: Level job to 18, do subjob quest, level subjob. Then level main job / subjob to 30 to get the quest(s) for the advance job you want to unlock.
"... and so I close, realizing that perhaps the ending has not yet been written."