Games should automatically update when you launch them if there is an update available.
All steam games update themselves automatically.
you cant Steam doesnt allow that
To cancel an update in Steam, go to your Library and find the game that is currently updating. Right-click on the game and select "Pause Update" or "Stop Update" from the context menu. You can also go to the "Downloads" section in the Steam client, where you'll see the ongoing update and can pause or cancel it from there.
In order to update Counter Strike: Source you will need to update the Steam system. See related links for more information.
If you have Terraria on Steam it updates itself once an update is available.
First go to the TOOLS Menu then select Network Update and follow the instructions.
You can either sign up to Steam and they will update the game automatically or you can download the Patches from the official SI Games website
Yes you can, you import and add non-steam games to your Steam library. From within the library you can launch and run any games, although 'Steam achievements' will only be available for Steam enabled games.
They don't. Only games distributed and managed by Steam can make use of the Steam API.
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.
Yes, you can import and add non-steam games to your Steam library. From within the library you can launch and run any games, although 'Steam achievements' will only be available for Steam enabled games.
No, atleast not that I've seen. (please update if you know different) The only way to get The Witcher 2 "Linked in" to steam is to buy it via steam.