my theory about and questions sin

Well we know that sin was created by Yevon,during the war between Zanarkand and Bevelle,but who was Yevon?
I think we was from Zanarkand,because Zanarkand is the land of the Summoners,and i think that he created sin to destroy Bevelle,in retaliation of the destruction of Zanarkand,that is revealed later in the game that was destroyed by Bevelle and not by Sin .So what happened?did the creation of Yevon go wild and start destroying everything ?And who was the first Sin. Since lady yunaleska did the first final summoning who was the first Sin?
And could the Al Bhed be people from Bevelle,that get exiled by the fist's Yevon Priests?

Yevon was the ruler (i think his title was High Summoner, or maybe thats me imagining things) of Zanarkand.

He created sin to protect him as a supposedly inpenetrable armour while he summoned Dream Zanarkand, and it appears that his armour is fond of causing death. I'm sure theres a reason somewhere, but I cant think of it.

Yu Yevon was the first Sin, he was at its core in the same way that the fayth of the final aeon was at its core. Therefore when yunalesca did the final summoning with Zaon as her fayth, Zaon then became Sin, since Yu Yevon soul, which was all that was left of him, possessed the aeon.

As far as I know, the Al Bhed could have been from anywhere, but where exhiled because bevelle had recently formed the Yevon church, and most Machina were outlawed, but they didnt want to gve up they're machina.

I'm sure someone will soon come along to fill in the gaps I've left, if these answers dont meet with your approval.

Well,i think that the Zanarkand Dream is something that is not related to Sin,i think that Yevon and the other summoners created the zanarkand dream to keep alive their
destroyed city, and the faith just want to stop it because they are tiered ... and the faith is dead summoners.
Another thing is if Bevelle was at war with Zanarkand and Yevon was it ruler ,how did they created the yevon religion?
And that religion is against machina,and bevelle was superior armed with machina.It's a little confusing .... Well all religions are ....

A lot of this is explained in the game, but here goes:

You're right, Dream Zanarkand has nothing to do with Sin. The fayth and Yu Yevon are what caused the Dream. Zanarkands survivors of the Machina war knew their city was doomed, so became the fayth on gagzet. They are not quite dead, but also not alive as far as I understand, but the fayth are people whose bodies have turned to stone, and whose soul is trapped.

Sin was created as an armour to protect Yu Yevon as he summoned from the fayth what is known as Dream Zanarkand. It is considered a dream I think because it is the dreams of the fayth that make it possible, and after 1000 years, you cant blame them for being tired.

The Yevon religion is told by maechen to be the result of a deal between Bevelle and Lady Yunalesca. She defeats sin and he gets eternal glory. It is also said to be a possibe way of lessening Sin's damage, as bevelle originally thought that Sin was being Summoned by Yu Yevon with the fayth on gagazet, so they wanted to try and suck up to him so he wouldnt set sin on them.

As for the machina, I dunno, It might be an attempt to try and prevent another machina war...

I believe Maechean explains most of that on Mt. Gagazet. I don't remember why the religion was created, but I know that the use of machina was forrbidden in order to prevent another war. Kinok says that this can be overlooked under certain curcumstances. (I think, I havn't seen that part of the game in atleast a year.)