The application opens in mid May -- it's not important, although it'd be cool, to have your AADSAS number be 1. You just want to have the thing out as early as possible before they get swamped with apps.
I'm pretty sure you are able to send in your transcripts even before the app officially opens.
Althought you can send in your LORs to AADSAS, you can also send them directly to all the schools you are applying to. This is what I did because after all I heard about AADSAS I didn't trust them.