I have even more lovely questions from my NG+ playthrough

First of all, what is Sabik? Lahabread mentions it in the dungeon but doesn't give any context as to what it really is, where it came from, etc. I've only done content up to 3.3 so far, so don't spoil it if it gets explained later. But I would like to know if it does get explained eventually

Second, If we could have rescued Minfilia from The Antitower, why didn't we try that with Y'shtola in the first place? Is it because The Antitower was unknown to us at the time?

Third, what was it that undid the Allagans? The Warring Triad questline triggered this question, as it seems a lot of their technology is still fully functional, or would be if the Allagans were still around. Once again, please just tell me if this gets explained later in the story, otherwise I would like to know lol.

Thank you!