LG Optimus G is LG’s late 2012 flagship phone. It is powered by quad-core Qualcomm Snapdragon S4 Pro processor. The speedy processor is backed by 2 GB of RAM, 32 GB of ROM, a 4.7″ “True HD-IPS+” panel, LTE connectivity, a 2100 mAh battery, and an 8 or 13 MP camera (depending on region). It originally came with ICS OS but it was upgradable to Jelly Bean.
LG Optimus G did not receive the official Lollipop update. However the CM team have created the CM 12.1 custom ROM which will update the device to the latest Android 5.1. This is the official version of the ROM and it contains very less bugs. If you want to install this ROM on Optimus G, follow the guide given below.