After being sick and tired of inconsistent performance of Samsung Galaxy Grand Duos, yesterday I decided to go ahead and install a custom ROM (firmware) on my phone. Since then, a few of my friends have shown interest in learning how to do that. Since majority of threads in XDA forums do not have a step by step procedure on how to install custom ROM on Galaxy Grand Duos, so I decided to write this blog post.
Please remember to back up all essential data from your phone to Google Drive or your PC, before installing a custom ROM. Also make sure you are running 4.2.2 firmware, in order to install Cosmic ROM, which is based on CyanogenMod 11 and supports dual SIM. This process also requires a windows PC for the initial step, so make sure you have that as well, along with MicroSD card installed in your phone with at least 300mb free space.
Files you will need
Copy files to SD card
Copy the zip file for Cosmic ROM and Google Apps into your phone’s external SD card (do not copy it to internal storage of your phone).
Install ClockworkMod Recovery with SELinux support
Now you need to install ClockworkMod Recovery on your phone, so boot into Odin mode by pressing Power + Volume Down + Home button. Once you are in Odin mode, let go of the keys and connect the phone to your PC.
Open Odin on your PC, make sure only Auto Reboot and F. Reset Time options are checked.
Under Files, click on AP and choose ClockworkMod zip file. Once Odin has done checking the file, click on start. After Odin is finished installing ClockworkMod, it will reboot the phone.
Install Custom ROM from ClockworkMod Recovery
Now you will need to boot into recovery mode by pressing Power + Volume Up + Home Button, once you are in recovery mode, let go of those buttons.
Use volume up and down key to scroll up and down. Choose “install zip option” and then press power button.
Now choose zip from /storage/sdcard1 and press power button again.
Now choose Cosmic ROM zip file and press power button and then press yes to install custom ROM.
Within few minutes, Cosmic ROM should be installed on your phone.
After the phone is done rebooting, go to Settings – Backup and reset – Factory data reset. This step is essential if you were using Samsung firmware before installing this ROM.
Enable Dual SIM Support
Go to app list and open Terminal Emulator.
Type SU and press enter.
Type setprop persist.radio.multisim.config dsds and press enter again.
Once done, reboot the phone and you should be able to use dual SIMs again.
Install Google Apps
After doing all this, you would have noticed that none of Google’s Apps are installed in your phone, including Play Store. To install the bare basics, reboot the phone into recovery mode by pressing Power + Volume Up + Home button.
Again choose to install from SD card and this time, choose the Google Apps zip file.
Once installed, reboot the phone and you will have Play store along with Gmail and a few other apps installed on your phone. Rest of the apps you can download from the Play Store and now you can start using your phone.
Disclaimer: There is always a chance that while flashing your firmware, you can cause damage to your phone’s firmware and end up bricking it. So make sure to proceed with caution and follow all the above listed steps. Also make sure to read everything that is written on Cosmic ROM thread on XDA, including existing issues you can possibly face.