I spent a day battling with getting a custom ROM on my Redmi 3 and gave up. In case anyone reads this: Xioami make amazing phones for the price. This $120 USD phone outperforms my S3. But getting a custom ROM on a Xioami is getting increasingly difficult - you have to ask for permission, jump through hoops to unlock the phone and sometimes it just does not work. Xioami is the Apple of China - great UI but increasingly closed ecosystem. Their OS is called MIUI, which is basically Android with more customization options (necessary for the markets they serve). It is a great phone and OS, but it is more complex than just flashing CyanogenMod (unfortunately).