i have google assistant working on my device. i don't know if you did this but go to settings/installed apps/defaults app settings /and set google default search engine and after this it should work just fine
1)you can flash 8.1.6.0 via twrp
2) link xiaomi.eu_multi_MI5_V8.1.7.0.NAACNDL_v8-7.0.zip
P.S. you can find all eu roms on this forum. click on the ROMs DOWNLOAD section above, and then click Download stable(the first link)
i don't think you had slow motion on redmi 3 pro. that feature is only available in high end phones like mi5 for example . i used to own an redmi 3 pro and didn't had slow motion video recording
this is a screenshot from your video. you can see clearly that all 4 cpu cores are online and working. leave the cpu-z app alone. it's an 3rd party app with false information in your case. Your cpu is working normally. Case solved!
what about it? i don't think there is a rom on xiaomi eu which has 2 cpu cores stopped. if you use cyanogen the may be some errors but on eu roms i don't think so
Cpu-z does not show the exact statictics on every device... so don't worry, the cpu is working normally! you can see the exact statistics on the settings menu/developer options/ show cpu usage
go to settings/battery/manage apps battery usage and make sure that the power saving mode is off (miui won't restrict background activities)
also you can lock the app in recent apps menu by swiping down on the app icon when in recents menu
i don't think you have to apply for unlocking your bootloader again. I accidentally got my bootloader locked again and i flashed latest global developer rom and unlocked with miunlock tool without a second request. the first one was ok
press all 3 buttons at once and wait until the second mi logo appears. after that release all the buttons and you should be in the second download mode(eld). after that just flash any official rom with MiFlash
it says clearly on the download section on this website that in order to flash xiaomi eu rom you need to have unlocked bootloader. so you need to unlock the bootloader ..it is very easy, send a request on the official mi website and wait a few days for an approval