Microsoft released the first build of its Windows 10 Mobile OS to a subset of Lumia devices.
But before you go ahead and install it on your Lumia, be sure to back up all your content (preferably to OneDrive).
Also since this is a very early build of the OS, it will be filled with bugs and instabilities, in fact here is a list of all the known bugs/issues from Microsoft with workarounds to some of them. Note these are known issues, unknown issues you will find out while you use the build on your device...
|Existing alarms will not be migrated to Windows 10||Reset alarms after upgrade|
|Wi-Fi settings don’t roam when phone is upgraded to Windows 10||Manually set Wi-Fi settings when on Windows 10|
|VPN not available in current Windows 10 builds. Setting will fail to launch. |
Coming in a future update
|Additional language keyboards may not be present and may not be able to |
install on US builds after upgrading to Windows 10
|Reopen the Windows Insider app and re-select Insider Fast/Slow again. The download of keyboard packages will then work|
|Photos app will fail to launch periodically when attempting to add a photo |
attachment to an email, OneNote or Facebook item.
|Try again. Succeeds after a few attempts.|
|Quiet Hours is missing the automatic rule that enables Quiet hours during |
calendar appointments marked busy. Also the setting “Anyone breaks through
if they call 2 times in 3 minutes” us unchecked but enabled.
|Apps are not displayed in Battery saver after the upgrade.||-|
|Access Point Names (APNs) in recovery images can fall out of date. |
For some phones/networks, this will block the cellular data and MMS
capabilities of a phone when recovering back to the base image.
|Before using the Windows Mobile Recovery Tool to recover, record the specific APN settings on your phone. Set manually once phone restored|
|Cellular data not working while roaming, despite enabling data roaming||The setting doesn’t work the first time it’s enabled. Turning off and then turning on again will enable data while roaming|
|Using a Bluetooth headset while playing back video results in low frame |
rate for video, due to a bug in the interaction between video playback and Bluetooth.
|Use wired headset for listening to audio when playing videos.|
|Sync to Microsoft Band doesn’t work after updating to Windows 10. If you have your phone synced to Microsoft band, it will not pair after the update to Windows 10.||After upgrade to Windows 10, go to Bluetooth settings, un-pair the Microsoft Band device and re-pair it.|
|DataSense resets data use history on upgrade to Windows 10.||No workaround. Will calculate correctly after the reset.|
|Trying to set lock screen picture will fail at times||Re-attempt the operation.|
|After upgrade, tapping on “Playlist” from start screen or from within Music App fails to play music. Playlists are greyed out.||-|
|Cortana tile and settings are missing on the start screen after upgrade||Go to app list and re-pin the tile|
And in case things go south fast, say your phone becomes bricked or unresponsive or you just don't like the build anymore, you can revert back to its normal state (before you installed the WP10 build) using the Windows Phone Recovery Tool, Microsoft provided.
Do note though, it isn't the same with Nokia Software Recovery Tool.
While the Nokia Software recovery Tool flashes your phone with the original firmware, it also wipes it clean. The Windows Phone recovery Tool on the other hand just reverts back to the state was in prior to installing the preview build and with all your content intact.
So check it out, it might come in handy...
Check out more info on the known issues on Microsoft Blogs