I have an Windows Phone app designed to work on WP 7.5. It was uploaded to the store long time ago and now i wanna update the app. I want to update the app for WP 7.5 and also create the same app for WP8. I'm doing the updates to the existing WP7.5 project and get the XAP file and then Upgrade the project to WP8 and the do some changes and get another XAP for windows phone 8. But my question is how can i upload both XAP file to the marketplace. Im not very clear about what should i do. if i do the above procedure, would i be wasting my time. I have another app that i updated for WP8 but not for WP7.5 my nokia Lumia 710 shows the older WP7.5 version of the app. I understand the logic behind that but can i update for both of the OS at the same time?