The XDA developers have recently released an unofficial CynogenMod 11 ROM for the Sprint Samsung Galaxy S3. CM 11 is based on Android 4.4 KitKat, so if you wish to experience the latest Android version alongside a handful of CM-based extra features, then this is how you do it.

This guide will enable you to install this unofficial CM 11 Android 4.4 Custom ROM on your Sprint Samsung Galaxy S3. Once again, please note that this is not an official CyanogenMod release. This is a pack developed and ported over to the Sprint SGS3 by XDA members and developers. As such, the ROM may contain bugs. If you want to learn more about the insides of the ROM, or you wish to see if other users have run into bugs, or simply if you wish to ask the developer something about the ROM, then visit the XDA thread by clicking this link.

IMPORTANT – PLEASE READ BEFORE PROCEEDING

• This custom ROM is designed only for the Sprint Samsung Galaxy S3. Do not attempt to apply this ROM to any other smartphone or SGS3 variant, or you risk damaging / bricking your device
• In order to apply this ROM, you will need to have a factory unlocked, rooted Sprint Galaxy S3. Your smartphone also needs to run at CWM Recovery (at least version 6.0.4.3)
• During the process, you will need to factory reset your device. As such, you may want to backup your data before proceeding
• You can use the "Helium" app to backup data from apps
• You can use the "SMS backup & restore" app to backup your messages
• You can use the "APN Settings Backup & Restore" application in order to backup your APN Internet settings
• Backup your contacts by syncing them with your Google account
• Before proceeding, you will need to enable USB Debugging. To do so, go to "Settings" > "About device" and then tap "Build number" until the "Developer options" menu becomes visible (you will get a message confirming this action). Then, go to "Settings" > "Developer options" and enable "USB Debugging"
• Before proceeding, make sure that your smartphone's battery is at least 60-70% charged. It is very important that your smartphone does not remain out of battery during the flashing process
• During the process, you should create a NANDROID backup (more details below)
• This is an advanced guide. If you brick / damage your phone, or if you lose data, you cannot hold the developers or anyone else responsible

Flashing the Unofficial CyanogenMod 11 Android 4.4 KitKat Custom ROM on the Sprint Samsung Galaxy S3:

1. Download the CM 11 zip file by visiting this link
2. Download the Google apps package by visiting this link. (Make sure it's the one weighing 245.5 MB, named "pa_gapps-full-4.4-20131126-signed.zip"
3. After the files have been downloaded, place them in a folder, but don't unzip them
4. Connect your smartphone to your computer using the USB cable (remember to enable USB Debugging)
5. Copy the zip files that you have downloaded, and paste them onto your phone's internal storage
6. Power off your device
7. Boot in CWM Recovery Mode. To do so, press and hold the "Volume up", "Power" and "Home" buttons at the same time. Then, remove the buttons once the recovery mode screen appears
8. You will now create a NANDROID backup. This will make a restore point on your device so that you can return to your current ROM in case you don't like CM 11 etc. This step should not be skipped! It's a safety precaution and it's worth doing!
   
   • To create a backup, select "backup and restore" from the menu, then name your file and save it on your device
9. Now you will need to factory reset your device. Select "wipe data / factory reset" and confirm your actions
10. After the factory reset, select "install zip from sdcard" > "choose zip from sdcard". Then, find the CM 11 zip file and flash it on your device
11. Once the CM 11 zip file is flashed, you will need to flash the Google Apps zip. Select "install zip from sdcard" aganin, but this time browse for the Gapps zip and flash it
12. After both files have been flashed, return to the main recovery menu
13. Reboot your smartphone in normal mode. NOTE: this first reboot after the flashing process can take a while. Be patient and don't press any buttons. In case the process does not end in 10 minutes, or if your handset is stuck in a boot loop, then you need to remove the battery, re-install it and start the tutorial all over again, without skipping any steps
14. Congratulations! After the reboot, your device should now run the unofficial CM 11 ROM
15. You can now login with your Google account in order to restore your contacts, and use Helium and the rest of backup apps to restore your settings and messages

NOTE: if you don't wish to keep CM 11 then you can restore your previous ROM by using the backup file that you have created at step 8