I'm almost lvl 30 with my Arcanist, and have my second class (Thaumaturge) at lvl 15.
I will be choosing a Summoner job.
My question is, when I choose the Summoner job. Will other cross class abilities, that I haven't unlocked, be locked?
For example: there's 3 skills from the Archer class, that a Summoner can use. But I haven't unlocked them.
Can I unlock the Summoner job at lvl 30, and then return to an Archer to unlock the wanted skills?
Or do I have to unlock the archer skills before I choose the Summoner job?

Thx