Step No 1:- First, connect your Galaxy Grand with the PC using its USB data cable.
Step No 2:- Copy the downloaded CM12 Android 5.0.2 Lollipop update file and Google Apps package to the Galaxy Grand.
Step No 3:- Disconnect your phone after copying files into it.
Step No 4:- Turn Off your Galaxy Grand in order to boot it into Recovery Mode.
Step No 5:- Now turn your device on by pressing and holding Volume Up + Home + Power buttons at the same time until recovery mode is being displayed.
Step No 6:- After entering into Recovery Mode, select “wipe data factory reset” and “wipe cache partition”.
Step No 7:- Also, select “Advanced” and choose “wipe dalvik cache”.
Step No 8:- Navigate to the main Recovery Menu and choose “install zip from SD card” followed by “choose zip from SD card”.
Step No 9:- Find and select the the CM12 Android 5.0.2 Lollipop firmware .zip file that you’ve already copied to your device. Proceed the installation process on your Galaxy Grand.
Step No 10:- Install Google Apps Package on your device by repeating the above steps.
Step No 11:- Reboot your device now by going to main Recovery Menu again and select “reboot system now”.
Done! You’ve installed CM12 Android 5.0.2 Lollipop custom ROM on your Samsung Galaxy Grand 2 successfully.