Android 4.3 firmware was caught running on Google Play Edition Galaxy S4 via leaked screen shots. Sammobile has shown the screen shots of first Android 4.3 test build firmware for Snapdragon-powered Galaxy S4 model GT-I9505G of Google Play Edition. Google has not yet publicly released the Android 4.3 OS. But OEMs has got an early access to the source code.
While just after showing the leaked screen shots, Sammobile has physically installed the latest Android OS version 4.3 that has build number “JWR66N.S005.130625“. But this test installation is made on standard Snapdragon-powered Galaxy S4. Yet Android 4.3 Jelly Bean OS is found fully functional on the S4 device.
But this test installation is only possible through Odin. You have to flash a custom ROM that will end your warranty. So it will be a risk, if you do not have enough skills to do so. Follow these instructions to download Android 4.3 OS for Galaxy S4. But keep in mind that Android 4.3 is still under development and will not have full features.