Sony Xperia Z2 was released in the first half of year 2014. It has a 5.2″ IPS LCD display, with a resolution of 1920×1080. it’s powered by a Qualcomm Snapdragon 801 processor, with 3GB of RAM, 16GB internal storage and a microSD slot. The Z2 has a 20.7MP camera, with 4K video recording at 60 frames/second. All this is powered by a 3200mAh battery.
Sony has recently started rolling out the Android Lollipop update to the Xperia Z2. But it is Android 5.0.x based and not the latest Android 5.1. You can install Android 5.1 on the Xperia Z2 using the CM 12.1 custom ROM. Follow the guide below.