For example, I have Deus Ex. I did not buy it on Steam, but if I added it to Steam through this option would I be able to have Steam download updates and patches for it like I did? I know you can buy Deus Ex on Steam anyway.
If the answer is yes, what about a game that I want to add to Steam that can't be bought on Steam, like Torment. Would Steam download all the official patches for me?