Thanks for quick reply. I've been checking the hub every day at daytime and I do not find the 2nd crystal. The first one I did find. Since I did not find the 2nd, there has yet to be a third.
Regarding 2B quest, I am level 37, and I got a scene when talking to the console etc... however nothing came of that. Not sure exactly why, no new quest, nothing.
Edit: Now got every scene for all girls (except 2B and Ahri which I cannot find / unlock) except for 1 scene with Marin which says needs continuation of story (no quests left to do and no more stars to do) and I think one other girl also had a similar scene as Marin that was locked behind story that doesn't seem to exist.
Edit2: I found the crystal and managed to find Ahri. It was NOT in the hub though. It was in the adventure guild.