Samsung Galaxy Mega 5.8 released in May 2013 with Android 4.2.2 Jelly Bean can now be updated to Android 6.0.1 Marshmallow. This update is possible via custom ROM developed by CyanogenMod. The CM13 custom ROM is unofficial but it has all the required features of Android Marshmallow and its AOSP as well.
So, the ROM is worth of trying for experience. But if you want to wait for the official Android 6.0.1 Marshmallow to be available for this 2013 device, then its not worth it as you are not going to get the update at all. The only way you can get the update is by flashing custom ROM.
But to flash the ROM, first you need to root your device and install custom recovery on it. Also, it must be noted that once you root and flash the custom ROM on your Samsung Galaxy Mega 5.8 its warranty will void.
Follow the steps mentioned below carefully to avoid damage to the device. If there is any damage to device during or after flashing the ROM you will be the only person responsible for it.
Preparing Your phone
- This information is only for the Samsung Galaxy Mega 5.8 GT-I9152 and do not try it on another device or you will brick the device.
- The Phone should be fully charged to avoid interruptions.
- Backup all the important data to some external medium.
- USB drivers must be installed on the computer.
- Make Nandroid back up of the current ROM to restore it in case anything goes wrong in the future.
- The Device should be rooted and its bootloader must be unlocked.
- Custom recovery tool like TWRP must be installed on the device.
- USB debugging must be enabled on the device. Go to Settings > Developer Options > USB debugging mode > Enable it.
Install Custom ROM based Android Marshmallow on Samsung Galaxy Mega 5.8
- Download the Android Marshmallow based unofficial CM13 ROM from here.
- Download Google App's from here.
- Transfer both the downloaded files to the device internal storage.
- Switch off the device and reboot it into Recovery mode by pressing and holding Volume Down and Power key for a few seconds.
- Backup the data and also make Nandroid back up in the TWRP recovery under Back up options.
- Wipe all the data present in device by selecting Wipe Data/Factory reset option in the recovery menu.
- Select the options on the next screen and swipe the button to confirm the action.
- Now select install option from the menu and navigate to Custom ROM file and select it.
- Swipe the bottom of the screen after selecting the file to flash it.
- Now similarly flash the GApps file.
- Reboot the device by selecting the Reboot option from the menu.
You device will now be updated to Android Marshmallow, to check the status go to Settings > About device.