Since OnePlus One is more than two years old, it is strange to receive any more official software update from the company. That said, phone owners can still be able to get the latest Download and Install CM 14 OnePlusOne via custom ROMs from Internet.
ALSO Read : How to Root Android Phone Without PC
[Disclaimer: This method is very technical and should be performed by a person with sound knowledge of rooting (or manual software installation) Android Smartphones. If step-by-step installation process is not followed properly, there are chances of the smartphone getting bricked or being permanently irreversible. mobfreak cannot be held responsible for any damage or claims from readers if the procedure does not return the required results or if the smartphone is bricked. Hence, users are advised to proceed with caution.]
Step 1: Download and Install CM 14 OnePlusOne custom ROM and Google Apps onto your PC.
Step 2: Connect OnePlus One to PC via USB cord.
Step 3: Move Android 7.0 Nougat AOSP (un-official) ROM zip file and the Google Apps .zip file into the smartphone’s storage memory. [Note: Users are informed to paste the .zip file in the storage root folder, not in any different folder.]
[Note: Before users’ start installing the custom software, be confirm that the device must have rooted and has installed ClockworkMod Recovery/TWRP tool.]
Step 4: Switch off the device and disconnect from the PC.
Step 5: Perform the normal Recovery Mode foray by press holding ‘Volume (Down)’ and ‘Power’ buttons.
Step 6: After beginning the RECOVERY mode, clean the phone memory, by selecting ‘wipe data/factory reset’
[Note: use ‘Volume’ keys to operate and ‘Power’ button to select options while working under Recovery Mode]
Step 7: Clean the cache memory by choosing ‘wipe cache partition’
Step 8: Drive back to ClockworkMod recovery, and select ‘advanced’ and tap ‘wipe Dalvik cache’ [Note: This move is optional, but many suggest this procedure so that user will not face boot loops or any other errors in the center of custom ROM installation]
Step 9: Return to the main recovery screen and then choose ‘install zip from SD card’
Step 10: Tap ‘choose zip from sd card’ and move to Android M ROM .zip file in SD card and begin the installation method. Repeat the same method to install Google Apps [Note: use ‘Volume’ keys to operate and ‘Power’ button to select options]
Step 11: Once done with the installation process, navigate to ‘+++++Go Back+++++’ and restart the phone by opting ‘reboot system now’ seen in the recovery menu.
Now, your device (OnePlus One) will take a few moments to done the booting process.
Users then head to ‘Settings’ >> select ‘About phone’ to verify the installation of Android 7.0 Nougat CyanogenMod CM 14 custom ROM.
Install CM 14 OnePlusOne custom ROM:DOWNLOAD