Doesn't look like the retail box will activate on Steam (the game itself is not a Steamworks title). But according to this, the downloadable version *might*. In that case it makes more sense just to buy on Steam to get the pre-order bonus. http://forums.steampowered.com/forums/showpost.php?p=33317702&postcount=4
This is not a steam game. I called Ubisoft to verify and only the version purchased within Steam will use Steam. All other versions work outside of Steamworks. I cancelled my Amazon order and have preordered via Steam.
1. The game launches through Uplay, but it can be purchased on Steam. Whether the Steam version launches through Uplay I do not know.
2. Not really sure what you mean here. The game is published by Ubisoft, so the only support it receives is through Ubisoft. If you purchase the Steam version and you have a problem Steam will most likely ignore your requests because this is a third party title on Steam and it is not created or published by Steam. So no, the retail copy that you order through Amazon is not installed through Steam, SADLY.
@Hawk23 Thanks for clarifying that for me. I know this is published by Ubisoft, but I was hoping that it was the Steam version and not Uplay. I don't mind Uplay, but Steam is a MUCH better game client, imo. I'll be getting the game anyways.