OnePlus One, the 2014 flagship killer, is truly an awesome phone. You can’t get a phone better than this in any respect at this price point. I am using this phone for a while now and I couldn’t find anything wrong with this phone that justifies the low price. CyanogenMod and OnePlus teams have put really a lot of effort to offer us an experience as close as possible to a Nexus. The phone also has a great developer community working constantly and bringing us new amazing ROMs. However, you might, sometimes, want to go back to the stock ROM CyanogenMod 11s, which itself is pretty nice. It offers a lot of customizability and very good and fluid performance. I am going to show the steps for restoring stock firmware on the 64GB OnePlus One.
For some reason, you might want to downgrade your HTC One from Android 4.4.2 to Android 4.3. For example, I updated my AT&T HTC One to Android 4.4.2 with Sense 6.0 by converting it to Developer Edition. After using it for some days, I wanted to revert it back to stock conditions. You might want to do it before returning it to AT&T for warranty or other issues. If you just try to flash a lower version RUU, you will most likely get error message. The problem results from the fact that higher Android firmware from HTC usually comes with a higher version of HBOOT. So, whenever you try to flash an RU.exe, it will show you error as it cannot flash a lower version HBOOT to a device which already has a higher HBOOT version. We need to manually flash a lower version HBOOT first and then use RUU.exe to return to complete stock.