Update Galaxy S3 I9305 to Android 4.3 CM10.2 Custom Firmware

The CyanogenMod unofficial custom firmware based on Android 4.3 Jelly Bean is being tried and tested by many Android users to check out the new features of coming AOSP official ROM based on the latest Android version. This unofficial nightly firmware is an early build of final CM10.2 firmware, hence you might get some bugs. This comprehensive tutorial will guide you in the process of flashing the unofficial CyanogenMod 10.2 nightly build based on Android 4.3 Jelly Bean for Samsung Galaxy S3 I9305 LTE.

Prerequisites to check before you Update Galaxy S3 I9305 to Android 4.3 CM10.2 Nightly:

Backup any important data from your Samsung Galaxy S3 as a complete wipe will be required during the flashing process.
Enable USB debugging option on your device: Settings > Development Options > USB debugging.
Galaxy S3 I9305 LTE must be rooted, unlocked and installed with a recovery tool like TWRP or CWM.
Your device must be charged to at least 60% of power.

Note: this tutorial is specifically focused on Samsung Galaxy S3 I9305 LTE; kindly do not try this guide on other Android & Samsung devices. This guide would be particularly helpful for those who want try the CyanogenMod ROM to see the new features of Android 4.3 JB.

How to update Galaxy S3 I9305 to Android 4.3 CM10.2 custom firmware:

Required files: download the CM 10.2 unofficial custom firmware zip for SGS3 i9305 from here and save it on your computer. Do not extract the contents.

Connect Samsung Galaxy S3 I9305 to your computer using a USB cable and copy the zip file to your phone’s SD card.
Disconnect the USB cord and power off your Galaxy S3 I9305 LTE.
Boot it into recovery mode and perform a Nandroid backup of your current OS; important step to revert back to current state. Go to Backup > backup and restore on ClockworkMod.
Wipe data operation: from CWM recovery menu, select wipe data / factory reset and confirm the process. You can skip this step if you are already on a CM 10.1 ROM.
From recovery menu, select install zip from sdcard followed by choose zip from sdcard. Locate the CM 10.2 Android 4.3 Nightly firmware zip and confirm the flashing process.
When done, follow the above step for GApps package installation.
Return back to main recovery menu and reboot your S3 I9305 into the new ROM. First boot takes a good 5 minutes so kindly be patient.

Awesome! You have successfully flashed the unofficial CM 10.2 custom firmware based on Android 4.3 Jelly Bean on your Samsung Galaxy S3 I9305.