Install Android 5.1 Lollipop on LG G3 D855 via CyanogenMod 12.1 [Unofficial] ROM

The unofficial CyanogenMod 12.1 custom ROM is now available to download for LG G3 D855 (International European Model). LG G3 is running currently the official Android 5.0 Lollipop update but the 5.1 update has not been released by LG yet officially and they have not announced that when the official build will be rolled out for G3 variant. But if you can’t wait and wish to get the latest Android 5.1 Lollipop on your LG G3 then we’ve given instructions to install the unofficial Android 5.1 update via CM12.1 custom ROM on your G3.

Do note that the current CyanogenMod 12.1 beta ROM is unofficial and released by LastStandingDroid (Senior XDA member), not by CyanogenMod team. This custom ROM is under development, thus like other beta versions, you may face some issues or not functioning features as the developer of this ROM (LastStandingDroid) has confirmed that data connection and Wi-Fi are not working in this build, so it can’t be used as a daily driver. But this CM12.1 comes with a lot of cool features, so if you want to experience the Android 5.1 beta firmware before the official release then follow then given guide carefully.


  • Contacts app force closes when someone’s icon is clicked
  • If data doesn’t work, restart the device for once
  • More to be added later when found

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This guide containing the Android 5.1 unofficial CM12.1 ROM and instructions are working with LG G3 (European Model D855) only. Do not try to install this beta firmware on any other device or incorrect variant. Check the model number of your device first.

Warning: will not be responsible for any kind of damage occurred to your LG G3 D855 during or after the installation of CyanogenMod 12.1 unofficial custom build. Proceed at your own risk.

Before Getting Started:

  • Create a proper backup of all your important data and settings before proceeding to the installation guide using a recommended custom recovery like TWRP or CWM.
  • Download and install LG G3 D855 USB Drivers on the PC.
  • Enable USB Debugging on the LG G3 on the PC by navigating to Settings > Developer Options > check USB Debugging option.
  • The LG G3 should be rooted with the latest version of custom recovery installed.
  • The bootloader of your G3 should be unlocked.
  • Check the battery level of your device, it should be charged at least about 80% to prevent unexpected shutdowns while installing the CM12.1 beta firmware.

Required Files:

Steps to Install Android 5.1 Lollipop on LG G3 D855 via CyanogenMod 12.1 [Unofficial] ROM:

Step No 1:- First, download the Android 5.1 CM12.1 unofficial build ( and Google Apps on the desktop of your PC.

Step No 2:- Connect your LG G3 to the PC via its USB data cable.

Step No 3:- Transfer the downloaded firmware and Gapps .zip files to the the root folder of the SD card of your phone.

Step No 4:- Disconnect the G3 from the PC and turn it OFF in order to boot into Recovery Mode.

Step No 5:- Turn ON the LG G3 while pressing and holding Volume Down + Power keys at the same time for a while until the LG logo appears, then release the buttons then press them again. Again press Power key 3 times to boot into recovery mode.

Step No 6:- While your device is now in TWRP recovery, create a Nandroid backup.

  • Select Backup
  • Do a swipe on the Swipe to Back Up option.

Step No 7:- Next, perform a full wipe including Dalvik Cache, Cache, System and Factory Data Reset.

Step No 8:- Once done, go back to the main menu of Recovery and select Install.

Step No 9:- Navigate to the unofficial CM12.1 ROM .zip file that you’ve already transferred to the root folder of SD card. Select it and swipe the Swipe to Confirm Flash option to begin the installation process.

Step No 10:- Go back to the main recovery menu and select Reboot > System after the installation is completed.

Step No 11:- Now, install Google Apps on your LG G3 by repeating the above steps.

Step No 12:- Reboot the LG G3.

LG G3 may take about 4 to 5 minutes while booting up for the first time after installation. So please be patient.

That’s All! You’ve successfully installed Android 5.1 CM12.1 Unofficial Lollipop custom ROM on your LG G3.


It is recommended that after the ROM is installed, give about ten minutes to the ROM once the LG G3 boots up for the first time.


If your LG G3 gets stuck on booting animation / boot loop after the ROM installation, then perform wipe dalvik cache and wipe cache partition for a few times before rebooting the device.


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