If you use this guide – How to root Redmi 2 natively? to root your Xiaomi Redmi 2, then you can follow this method to unroot. Else you need to install a clean fastboot ROM to do so. Anyway, just choose the method that you prefer to bring your Redmi 2 back to original stage again. Native unroot process is the same as rooting. But you need to use the unroot update file instead of rooting file. That’s it. Basically, it is okay to have root access on your Android device unless your applications (like banking app) do not work on environment with root access. Then you have no choice but need to unroot. Else just leave root access there.