Samsung Galaxy S4 released in March 2013 comes with two different versions – octacore processor and quadcore processor. Galaxy S4 i9500 is the octacore version having a Quad-core 1.6 GHz Cortex-A15 & quad-core 1.2 GHz Cortex-A7 processor. It has 2GB of RAM with 16/32/64 GB internal storage along with an expandable microSD card slot.
Galaxy S4 i9500 ran on Android 4.2.2 at the time of its release and it is upgradable to Android 4.3. But you can update it to the latest Android 4.4.1 with the CM 11 custom ROM. You will need root access as well as custom recovery to flash the CM 11 ROMs. Follow the instructions given below.