I've been installing and testing a lot of custom ROMs recently on my Redmi 2. This is a brief tutorial describing all the steps involved in installing a custom ROM (with specific steps required for Redmi 2).

Before proceeding, make sure you have backed up all your important data to another device.

Custom Recovery

Most custom ROMs require a custom recovery. In this section, I will provide the steps for installing the most popular recovery nowadays - TWRP.

  • First step is to install the Android SDK platform tools which include the fastboot command. fastboot is necessary for installing the custom recovery. You can get the platform tools for most OS here. If you are on Ubuntu, there is a very convenient package.

    If you have downloaded the platform tools manually, extract the archive to a directory of your choice, and open up your command line/terminal in the said directory.

  • Switch off your phone, and enter fastboot mode by pressing the volume down button and power button simultaneously. Connect the phone to your computer using a USB cable.

    In your terminal, type fastboot devices to make sure your phone is being detected. The output of the command should list your device. If not, check your USB cable connection. If it is still not being detected, you may have a broken USB port on your phone or a broken USB cable.

  • Download the TWRP image from dl.twrp.me/wt88047/. (Note that the image is for wt88047 which includes the following models - 20148(11/17/18/19). I'm not sure if this image works on wt86047 (2014813). You can find an appropriate TWRP image on MIUI or XDA forums. Note down the path to where you have downloaded the image.) It will be convenient to copy it to your current working directory.

  • Now, flash the recovery using the following command:

fastboot flash recovery /path/to/twrp/image
  • If you restart your phone now, MIUI may rewrite your recovery. Instead, you should reboot directly to your new recovery once before rebooting to MIUI. This can be done by
fastboot boot /path/to/twrp/image
  • That's it. You have successfully installed a custom recovery. You can now reboot into MIUI from the recovery.

Firmware

  • You have to ensure that your phone has the correct firmware version. Some (actually, most) ROMs require the Lollipop (Android 5.x) bootloader. If your MIUI is already on Lollipop, you can skip this section. If your MIUI is on Kitkat (Android 4.x) or lower, you need to flash the Lollipop bootloader. The requisite zip files can be found in the Lineage OS thread at XDA by nicknitewolf. I'm reproducing the links here - wt88047, wt86047.
  • Copy the zip file onto your phone's SD card. Reboot to your custom recovery (Switch off your phone, and press volume up, volume down, and power buttons simultaneously). Choose the Install option which will take you to a file browser. Find the zip file you just copied and select it. In the next screen, confirm that you want to flash this file. That's it. You have successfully updated your firmware.

ROM

Whichever custom ROM you have chosen should have detailed installation instructions. I will provide the general steps involved in flashing a new ROM here.

  • Download the zip file for the ROM, and get the appropriate Google apps (GApps) from opengapps.org. Copy both zip files to your phone's SD card. Reboot into recovery (power off, and press vol. up + vol. down + power).
  • Choose the Wipe option in recovery. Choose the Advanced wipe option in the next screen. In the following screen, select Dalvik/ART Cache, System, Data, and Cache. Confirm that you want to wipe the selected partitions.
  • Next, go back to the home screen of your recovery, and choose the Install option. In the file browser, find your ROM zip and confirm its installation. Once the installation is done, choose Install again, and select your GApps zip in the file browser. Wait for the installation to finish, and reboot. You should now be greeted by the boot animation of your new ROM.
  • That's it. Enjoy your new ROM!