It is widely expected that Google will start rolling out the Android 5.0 Lollipop update to the previous generation Nexus devices from today. While the company is yet to make any official announcement on this front, Nexus 7 (2012) owners have received the next best thing — the Lollipop factory image.
The download link of the factory image comes straight from Google’s server so it is as genuine as things can get. The Lollipop build is based on the LRX21P build, which is what the Nexus 9 also runs.
The factory image is only for the Wi-Fi variant of the Nexus 7 (2012), so you are out of luck if you own the 3G variant of the tablet. You can download the factory image from here but you will need to know your way around ADB and Fastboot to install it.
You can flash the factory image on your Nexus 7 (2012) by following the steps mentioned here. However, keep in mind that this will wipe the device of all your data, including app data and your personal files.[Via Android Police]