OnePlus says that manually updating the OnePlus One to OxygenOS 2.1.4 will result in the loss of all of your data, so back up what you can. In addition, once the bootloader is unlocked, the integrity of your phone cannot be guaranteed by the manufacturer. Do not flash the new OxygenOS build through TWRP or else your handset's unique IMEI number will disappear, and that could end up in an epic battle with OnePlus tech support.
Now, we hate to be the bearer of bad news, but OnePlus One owners will not get feature parity with OnePlus 2 owners. The proprietary sound technology from MaxxAudio is not available. Manual camera settings and RAW file capability are not offered with the OnePlus One. Fingerprint scanning is also out, and you can not adjust the color temperature of the screen.
What will be available to OnePlus One users is the Dark Mode with different accent colors, custom icon packs, and the double-tap-to-wake capability. With the Marshmallow-esque App Permission feature, you can control the information that each app has access to by approving permissions on a feature by feature basis. The version of the OS for the OnePlus One has been made specifically for the device
If you want to give your OnePlus One a software update and put some spring back into its step, click on the sourcelink. But be careful when flashing OxygenOS 2.1.4, as one false step could leave your phone without the Oxygen it needs to live.
source: OnePlus via AndroidAuthority