So... is she alive or isn't she?

I should know better than to expect to understand everything in a Japanese video game. If nothing else, I should have learned that from Katamari Damacy. But dang it, when I've spent hours and hours and hours of my life watching cut scenes and fighting the same impossible boss again and again, I want some closure at the end of a game. Did FF7 deliver that?

Um, not really.

I spend an hour fighting various incarnations of Sephiroth/Jenova, during which the sun goes supernova approximately 20 times, something I'm sure the astrophysicists would be surprised at. I've spent at least a year- or has it been two years?- playing this game on and off, which involved me playing up to the final boss twice. I've had my mind messed with, I've had to play though a scene where my character took a bath with, like, 20 other guys, I've cried at predictable moments. About the only thing I haven't done is raised or raced chocobos, at least not any more than I could help.

So here's what I want to know:

Is Aerith alive? Is she half-alive? Did she, in her dying moments, excrete her soul into a shiny ball that dropped into the planet's core, and is that what's alive? If Cloud really wanted to meet her in the Promised Land, shouldn't he just have let go at the edge of the cliff, so he could drop in and see his ain true love?

Also, Zach. What is the story with him? How much of Cloud is Cloud, and how much is Zach? If Zach was the cool soldier boy, how come Cloud turns out to be the one who defeats Sephiroth? What happened to Zach? And, since my characters seem to understand all this much better than I do, why don't they breathe a word of it to Zach's parents? I mean, that's just cruel.

Could someone please explain to me the difference, or relationship, between Holy, the Planet, and Lifestream? Which one is Aerith controlling from her semi-undead intraplanetary state?

Tifa? Seriously, Cloud ends up with Tifa? That would be like, like, like Harry ending up married to Luna. Wrong, wrong, wrong. (I just typed "wroung" three times in a row.)

I understand there are sequels to this game, including, I think, the movie Advent Children. Clearly, I am going to have to do some more research, because I'm coming out of this game with no clear sense of what happened in it.