Umm, Before Crisis should take place before Crisis Core... although it sort of connects with it (I think the scene with Zack/Cissnei at the beach is present in BC as well.)
And wth, Sephiroth doesn't kill Zack.. >.> And the Crisis isn't him summoning meteor, he doesn't do that until the end of FF7. Seriously, did you even play any of them? lol...
Now, Starr.. just play the game, everything is explained (in fact, it's explained extremely well..)
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