Plug in t AC and make sure your battery level is good.While you wait to make sure it charges up to a decent amount (over 50% is recommended, use your knowledge of charge times to estimate) download the Windows Phone Recovery Tool.
https://forums.windowscentral.com/e...singleTopic%26topic%3DFA142987&token=__Wp1Q9v
When you are ready plug the phone into your computer's USB and use the tool to revert to official. If you want, you can try again later to get it to 10.
It may help to remove the SD card and SIM before flashing and when upgrading. YMMV
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