Yes.
You can fix Skyrim on steam by removing all mods and Workshop content from your game before calling Skyrim support.
Yes, Skyrim was available to purchase and download from Steam on 11/11/11. Even hard copies of Skyrim had to be authenticated on Steam.
Steam's mandatory for Skyrim, for both disc and digital versions. If you've uninstalled Steam, you'll need to reinstall it, and get the patch from there.
You don't need to buy Skyrim from Steam, but it does need to be linked to your Steam account (by registering the serial code you should have got with the game).
Yes, you download it from Steam after you activate the game.
Skyrim DLC for PC is out as of 8/2/2012 in the Steam Store.
Yes, some. Not all of them can be activated on Steam. See the related links for a list of the games that can be activated on Steam and for the instructions on how to activate a game on Steam.
Check steam tech support.
There are hundreds, if not thousands, of Skyrim mods. A mod is a game modification that alters the game in some way, be it mechanics, appearance or behavior. 2 places where you can find mods for Skyrim are Nexus Mods and the Steam Workshop (assuming you have the Steam version).
Skyrim's system requirements were announced on the 25th of October.
Yes, you can purchase and download it from Steam.
you already have it if you have team fortress 2 or skyrim. go into tools and find it. you may have to download it.