1) You'll just toggle "show pre-release versions" in Impulse to see the beta update, at which point you can download it and play it.
2) Anyone, by the sounds of it.
3) Yes, it will override the current install. You should be able to make a copy of your Elemental folder, then apply the beta patch. In theory, the copy of the 1.09 folder should still work so you'd be able to launch it, and the actual installation will be updated to the 1.1 beta.
