If you are a developer who is developing Windows Phone 8.1 apps for the first time or if you are a beginner then you might have this question.
Can i run Windows Phone 8.1 Project on Windows Phone 8 device ?
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.