This is what Microsoft should’ve done from day one of Windows Phone
|Microsoft is allowing developers to access the pre-release builds of Windows Phone starting later today starting with GDR 3 of Windows Phone 8. They should have eliminated the route of carrier dependent updates for developers. This way developers would get latest bits of the platform and they could test on their devices, nail any issues and breakings and update their apps. Of course, in order to update your device, it has to be developer unlocked. You could developer unlock your device by joining Windows Phone Developer program or a registered Windows Phone App Studio developer. You could register yourself for Windows Phone App Studio here. Microsoft is saying this GDR 3 doesn’t have any new APIs and thus there will be no new SDK, and also it will update only the Microsoft part of the Windows Phone 8. Microsoft is cautioning “When you opt in and apply a prerelease update, you can only move forward with updates. When the update is publicly released for your device, you will once again be in a ‘released state.’ There is no path back to a prior release/update.” Also “After you install a preview update, you may void any warranty from your MO and OEM. In the unlikely event you run into an issue after you apply the prerelease update, you can visit the preview program’s support forum.”
Source: Windows Phone Developer Blog