I am very much confused about these. I would like to develop app for windows 8 , Windows RT , and windows mobile. I have windows 8 OS installed in my laptop. As far as I know, Windows RT is for ARM based devices. HERE ARE MY QUESTIONS: I develop an app, and put in windows store. Will that can be downloaded from a ARM based device ,which runs on Windows RT, AND from a windows 8 laptop , and same from a Windows 8 mobile? OR should it be different apps ?