To make "un-offical international" version work on my phone I simply copied this version over the stable with TWRP..
I also found I can easily revert to a stable release by using mi-flash again.
It is important not to root the device, so don't install SuperSu on your device, otherwise stop reading further.
I use TWRP only to copy the eu image over the original one.
Before you start the flash procedure you need to ensure your PC can communicate with your phone, so please ensure all drivers are installed before you start, otherwise stop here.
Also ensure you can copy data to your device, otherwise stop here.
If your device is not usable as storage device then surely something is wrong and will go wrong once you start the flash procedure.. Don't continue.. Solve this issue first.
The below procedure only works for the stable Version, but be warned, never use the developer verion or a rooted device!
Stop reading if either of this is true. It does not wirk for rooted or devloper versions.
If you are unsure stop - I cannot offer further support as I'm also new to Xiaomi devices!
Steps:
0. Read all instructions for TRWP, Mi-flash, and fastboot and ensure you understand them.
I take no responsibility this procedure works for your device. It's on your own risk.
Again, everything below is on your own risk, I don't take any responsibility! Be warned!
Read before you start, read all information about mi-flash and TWRP and understand how you can use TWRP to apply an image.
1. Search for latest official cn version and download it is the procedure for replacing stable versions.
http://en.miui.com/a-234.html
use Xiaomi Mi 4c Latest China Stable Version Fastboot File Download
I've used: libra_images_V7.1.6.0.LXKCNCK_20151209.0000.6_5.1_cn_9d4af16e6c.tgz
Unzip the package to a folder, use Mi-flash to flash this version, mind to use "Flash all"!
2. Reboot
3. search for the same eu version (MIUI Version numbers must match!) and download
https://www.androidfilehost.com/?w=files&flid=46986
I've used xiaomi.eu_multi_libra_V7.1.6.0.LXKCNCK (libra is the Mi4c image)
copy the zip to your device download folder
4. Download TWRP
5. Install TWRP - it is only used to copy the eu image
http://en.miui.com/thread-166465-1-1.html
mind to not install supersu it will break your MI4c device if rooted.
don't wipe system!!!!
6. start into TWRP
only wipe cache, data, dalvik - nothing else!
http://en.miui.com/thread-200444-1-1.html
7. copy eu image onto device
8. apply the image with TWRP
9. reboot
additional languages should now be available!
10 Configure your mobile and enjoy
You can easily restore to a stable version using Mi-Flash.