The official Android 6.0.1 Marshmallow has been released for various smartphones that were released in the last two years, while the Galaxy S3 models have been left behind and long forgotten by Samsung's Update service.

If you are still looking to run Marshmallow on your Galaxy S3 LTE I9305, then you can choose to flash a custom ROM like the one built by Resurrection Remix team. The RR Marshmallow 6.0.1 ROM is based on AOSP Android 6.0.1, CyanogenMod builds, slimROMs, Omni and on previous original Remix releases.

Here are main features that you will find in the Resurrection Remix Marshmallow custom ROM: Dark Material Theme, Quick-Smart pulldown, heads up, lockscreen shortcuts, battery mods, clockcolor options, ambiant display, network traffic monitor, quick unlock, and others more.

Check the following guidelines listed below in order to make sure that your device is supported by the tutorial:

  • use this post only with the LTE variant of the Samsung Galaxy S3.
    - the model number of this device has to be I9305.
    - check the version of your phone under Settings> About Phone.
  • do not attempt to update any other devices that you will find in this post.
  • your phone has to be rooted and it should be running the latest version of either CWM or TWRP Custom Recovery.
    - the installed Recovery has to be upgraded to its latest version, so that it supports the new Android 6.0.1-based custom ROMs.
  • in the tutorial part of this post you will find two extra preparation steps like the NANDROID Backup and the Factory Reset ones.
    - the NANDROID Backup creates a full restore point for your device, one that you can use in case the new ROM doesn't boot in normal mode.
    - the Factory Reset process wipes clean the system partition, but it won't delete any data from internal storage.
    - factory resetting the device won't remove any data from its internal nor external storages.
    - do not skip these steps.
  • in case you need to save any files from installed apps you should use the Helium tool for Android.
  • read the entire post and make sure not to skip any steps that are listed below.
  • check the battery charge level of your phone and make sure that it is over 50%, as it will prevent the device from powering off during the installation process.
  • this installation process is destined to be applied by advanced users, as we cannot be blamed in case you brick the phone nor in case you lose any important data in the process.

Now that you know all of the above you can continue to the next part of this post and learn how to successfully flash the new custom ROM for your device.

How to flash Resurrection Remix Android 6.0.1 ROM for Galaxy S3 LTE I9305:

  1. Download the RR Marshmallow 5.6.6 ROM build from here.
  2. Download Gapps for CM 13.0 ROMs from here.
  3. Transfer both zip files to your phone's internal storage.
    - after the files are copied you can disconnect the device from PC.
    - do not unzip the files.
  4. Power off the Galaxy S3.
  5. Boot it in Custom Recovery Mode.
  6. Start the NANDROID Backup for the ROM that's installed on your device:
    - CWM: select 'backup and restore'.
    - TWRP: select 'backup'.
    - set a name for the backup file and confirm process.
  7. Factory Reset the device:
    - CWM: select 'wipe data/ factory reset'.
    - TWRP: select 'wipe' menu.
    Confirm the factory reset and continue to the next step.
  8. Begin the Resurrection Remix 6.0.1 Marshmallow installation:
    - CWM: select 'install zip from sdcard', then 'choose zip from sdcard'.
    - TWRP: select 'install'.
  9. Find the RR M 5.6.6 zip file and confirm the flashing process.
  10. After the custom ROM is done installing on your phone you can flash the new Gapps zip in the same way.
  11. Reboot your device in normal mode and wait for the first boot process.
  12. Use your default Google account in order to regain complete control over your device.

These were all the steps that you had to take in order to complete Resurrection Remix Marshmallow custom ROM installation on your Samsung Galaxy S3 LTE I9305.

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