Is it possible to install pure (not manufacturer modified, without Emotion UI) Android version (4.2 to 4.4) to Huawei Ascend P6? If above is possible, is it possible to recover original Huawei Android version (with Emotion UI)?
You could try custom roms like Cyanogenmod or AOSP. I've checked Cyanogenmod site and there is no official build available for your device. However there are both unofficial Cyanogenmod and AOSP built for p6 on XDA-Developers Original Android Development. To install custom rom,
- Unlock your p6 bootloader.
- Install Custom Recovery like TWRP or ClockWorkMod [Look in above XDA-Developers Original Android Development forum link].
- Nandroid Backup your Huawei ROM from custom recovery so you can restore it later when you want to.
- Download custom ROM from XDA-Developers Original Android Development forum.