"...Big change in installation process of our ROMs (Must read it, otherwise you will cry on forum here and we will dont care):
- Xiaomi forced us to generate own keys for signing ROMs if we want continue to use their OTA service (again calling it "security improvement"). That means, our ROMs will not be possible to install via MiRecovery anymore (even on old devices like Mi2 or Redmi 1S) but only via TWRP/CWM...
- Our ROMs now contains TWRP which will install it automatically and overwrite your MiRecovery (If you still use it)
- For manual TWRP installation, we made a flashable ZIPs here so just install it via Updater up like any other update zip... (if it will fail, just unzip it and flash via Flashify app)
- Version 6.2.25 still can be installed via MiRecovery but it will overwrite it to TWRP
- Next versions will require TWRP for all devices..."
OK. Try to download one older multi developer ROM. Like this: http://miuif.celogeek.com/5.12.31/xiaomi.eu_multi_leo_5.12.31_v7-5.1.zip
And change this name to update.zip, put update.zip to rootfolder of your phone, after try to install this older ROM across MiRecovery. First Wipe cache, next Wipe user data, and last Install update.zip.
If success old ROM will contains own root in Security app / Permissions menu / Root access submenu.
A you can install Flashify from Play. You will can give root acces to Flashify.
And you will can install new TWRP with Flashify.