Tutorial to Root XXELLA Android 4.1.2 on Galaxy S3 I9300 Official Firmware
Step 1 - First thing that you are required to do is Download CF-Root-SGS3-v6.4.zip for Galaxy S3 to your computer and after that extract the zip file.
Step 2 - Second thing Download ODIN v1.85 (if required) that will help you to install Android 4.1.2 on Samsung Galaxy S3 I9300.
Step 3 - You are required to switch OFF your phone. After that go to Download Mode on your phone. The question arises that How? The answer is simple that Press and hold the Volume Down + Home buttons simultaneously, and after that press the Power button till you come across the construction Android robot and a triangle. You are required to Press Power once again in order to confirm to enter into Download Mode.
Step 4 - You must ensure that you have your Galaxy S3 USB drivers that are installed on your computer.
Step 5 - 5th step is to open ODIN on your computer. And after that connect your phone in order to your computer while your phone is in the Download Mode.
Step 6 - If your phone is successfully connected, one of the ID:COM boxes will turn yellow with the COM port number as an indication. This step is likely to take some time.
Step 7 - Now select the root package file that you have to flash/install on your phone. These files are to be found from the extracted file in Step 1.
Click on ‘PDA’ and select the file CF-Root-SGS3-v6.4.tar.