If you upgraded to windows 9, uninstalling it will revert back to windows 8.
Like Hell it will. It deletes it completely from your computer. What MS (BS) course did you hear that at?
Windows 7 comes with IE8 installed. One of the available windows updates, is an upgrade to IE9. If you want to go back to IE8, all you have to do is go to the control panel, view your installed updates, and remove the IE9 update.