Microsoft had always maintained backwards compatibility with most of their products.Compatibility has been one of the main reasons Windows has seen such great success,But unfortunate it wont work for windowsphone.I mean all higher version OS apps can't run on below versions.
Ex:If you develop a app targeting Windows Phone 8.0 , then this will run on Windows Phone 8.1 device but if you are developing an app targeting Windows Phone 8.1 , then it will not run on Windows Phone 8 device.
