Samsung Galaxy S3, the 2012 flagship smartphone will not receive official update of the latest Android version 4.4 KitKat anymore. Nevertheless, you can enjoy KitKat on the GT-I9300, using custom ROM CyanogenMod 11.
The reason that the Galaxy S3 doesn't support the official update is that the memory configuration of the smartphone would not allow. That's a shame because the KitKat supposed to be resource-efficient than its predecessor, Android 4.3 Jelly Bean, which the Galaxy S3 is currently running. Reason should logically be the numerous adjustments and additional apps that Samsung delivers with its TouchWiz interface and require more memory than of the device.
But there is still a possibility to use the latest version of Android KitKat on the Galaxy S3, is by switching to a custom ROM, the popular CyanogenMod , Android 4.4.2 KitKat based version CM11 is available for many devices and brings a stable and significantly more oriented towards stock Android KitKat on the Galaxy S3, as we know it from Nexus devices.
Important: This procedure applies only to the regular S3 (GT-I9300), not the LTE version (GT-I9305).
For rooting you need CF AutoRoot , at least if the device is running on Android 4.3.
Immediately after CF Autoroot, flash a custom recovery to the device. The latest version of TWRP file and flash in the same way as CF-Root/CF-Autoroot by ODIN.
As for flashing ROM using the KitKat-based CyanogenMod 11 – either the latest nightly build (experimental, potentially less stable) or the last snapshot (stable).
For the Google Apps you need a gapps package , best one from PA. We recommend the "Mini Modular Package" to flash and then subsequently install any other needed Google apps from the Play Store.
After flashing you have your Galaxy S3 on the latest KitKat stand. If, however, something goes wrong, the unit can be flashing by a stock firmware via ODIN ( here a firmware archive to reset, select the DBT version) to factory defaults.
If you have any problem leave a comment below.