i'm not sure where this should go but since am using Win8.1 Pro, here it goes:

how does one prevent any application's window from stealing focus while you are working? it's too often that, say, i'm working on Word and then something pops up and you find yourself typing on the wrong window (most specially embarrassing when you're chatting with someone and you type on a different window).

Hi,

Here application you meant is Windows Store APP, isn't it? If that it is, there is Windows setting to turn off app notification:

PC Settings\Search and apps\Notifications