How to install kitkat in oppo?
There are a few things which don't sound quite right.


4GB RAM - The Oppo R5 has 2GB RAM build in. 
"eight core MT6592" - R5 uses an Snapdragon SOC. MT6592 is an Mediatek SOC.
The Android version. It doesn't matter which version is shown in the system information. It's a simple edit in /system/build.prop. Everyone can write whatever they want.


With these things in mind I think you have bought a fake R5.
So can you change to Cyanogenmod? No. By installing the cyanogenmod for the official R5 you might brick your device as the kernel is not fitting your hardware. 

Link to the official product page of the R5