As you know, each time a new custom ROM firmware, suitable with the Galaxy S3, is being developed by third party devs, the software is provided only for one version of the handset, for example for the I9300 variant, or for the Verizon one and so on. So, the S3 users have to wait for the proper update to be released.
Anyway, today I will show you how to update your SGS3 with a new Jelly Bean 4.2.1 based ROM that can be applied on almost all the versions of the phone; the CM10.1 powered Illusion ROM can be easily installed on the Verizon, AT&T and T-Mobile Galaxy S3, so if you want to flash the same on your smartphone, check the following step by step guide.
Now, the present OS improvement has been released by those of xda-developers and brings a lot of new features and capabilities for your Galaxy S3. The best is that the Illusion firmware is based on the CM10.1 platform which means that the latest Android 4.2.1 Jelly Bean and CM10.1 features will be ported and added on your phone. The update is still in development stage, but don’t worry as you can safely use it. There are only few reported bugs and issues (camera, headphone jack not working during calls, lockscreen shortcut force closes, tethering, and MTP support) which of course will soon be resolved.
In order to conclude, here is what you need to know about the Illusion update: it is an unofficial software that has nothing to do with Samsung, so a manual installation procedure must be performed (you cannot OTA or by using KIES apply the same); it can be flashed on the Verizon, AT&T and T-Mobile versions of the Samsung Galaxy S3; it is based on the Jelly Bean 4.2.1 OS and will bring features ported from the popular CM10.1 custom ROM firmware; before updating your phone with the Illusion system you have to prepare the device by completing the following pre requisites.
First of all, you must root your handsets. Therefore choose a suitable root guide for unchaining the internal system of the Verizon, T-Mobile and AT&T Galaxy S3.
Be aware as by gaining root access the warranty will be lost. Always use a step by step guide, like the present one, don’t perform things by yourselves because you can end up in bricking your phone.
Install a custom recovery image on your smartphone, like CWM recovery; again use suitable tutorials with your AT&T, T-Mobile and Verizon Samsung Galaxy S3. The CWM recovery tool is important for us because it will be used on the update operation, so don’t skip this section.
Also, remember that this is a complex and risky operation not to mention that a full wipe of the system will have to be applied; that’s why you must backup the SGS3 data before going any further. Save the contacts, messages, call logs, market apps, EFS folder and anything else you need to.
It is also recommended to make a Nandroid backup too; in this way you will be able to restore the stock ROM in case you don’t like the new Jelly Bean software.
Up next, you need to ensure that the required tools and things (which will be used on the update process) are near you. For that we have another list of tasks. These are the general pre requisites that are being used each time you want to apply custom ROMs. So, if installing beta firmware on an Android based handset isn’t something new for you then you can skip the next part. If not, read carefully and complete the steps from below.
Make sure that you can use a Windows running computer or notebook that has internet connection enabled.
You will have to connect the Galaxy S3 with the computer so the USB cable should be near you.
The installation procedure will take a while so make sure that the phone’s battery is charged (if there is less than 60% power left).
Also, for avoiding the unpleasant situations it is recommended to temporarily deactivate the Firewall and antivirus protection that is running on both computer and smartphone.
On your S3 enable the USB debugging option.
And complete this step by step guide only if you want to flash the CM10.1 based Illusion Android 4.2.1 Jelly Bean custom ROM on the Verizon SCH-I535, T-Mobile SGH-T999 or AT&T Samsung Galaxy S3 SGH-I747.
How to Update Verizon, AT&T and T-Mobile Galaxy S3 with CM10.1 based Illusion Jelly Bean 4.2.1 ROM Firmware
First download the proper update file for the version of your handset.
The download link for the Verizon Galaxy S3 is here, for the T-Mobile handset here and for the AT&T device here.
Also, download the Google Apps package from here as it is not included in the update file.
Save all the downloaded files on the computer first.
Then, copy-paste the same on your phone’s SD card; for that you will have to connect the device with the computer via USB cord.
Unplug the USB cable and then turn off your smartphone.
CWM recovery mode must be reached therefore reboot by pressing the Volume Up, Power, and Home buttons.
Remember to complete a backup; up next from the recovery menu select “wipe data factory reset”, “wipe cache partition” and “Wipe Dalvik Cache”.
Return to the main menu by selecting “+++go back+++”.
Then select “install zip from sd card” followed by “choose zip from sd card”.
Pick the update file and start the flashing operation.
In the end repeat the step and install the Google Apps package too.
When done, select “+++go back+++” and “reboot system now” for ending the tutorial.
Congratulations, you have succeeded with the update operation. Your Samsung Galaxy S3 has been successfully updated with the CM10.1 powered Illusion Android 4.2.1 Jelly Bean Custom ROM firmware. Test the software and share the issues and bugs with us and with other users by using the comments area. If there are bugs, don’t worry as we will update you with a new tutorial as soon as an improved version of the update will be made available. Remember that the software is being provided by those of xda-developers, so we have to thanks them for the present step by step guide.