Ad. 3
Stock Miui = China Rom, you don't need the lazyflasher but you should "format data/factory reset" before flashing(twrp) or with MiFlash - wipe all & flash.
Data partition will be encrypted.
Ad. 4
Yes, you can wipe cache & dalvik.
Btw: Miui isn't odexed and it does not matter with wipe...
https://xiaomi.eu/community/threads/8-11-15.47621/
From the OP(1st post):
Installation via TWRP:
- Download zip to internal storage
- Updater - Menu (...) - Reboot to Recovery
- Install - Select zip
- Reboot
- Done
We have two dedicated Custom Roms - LOS 16 and Mokee:
https://forum.xda-developers.com/mi-a2-lite/help/double-tap-to-wake-t3826918
and much more Treble Roms(Arm 64 A):
https://forum.xda-developers.com/project-treble?nocache=1
I'm on AICP from begining.
8.11.1 build is one of the best for bettery life I've ever had.
I think your problems are from synchronisation with Xiaomi account, I don't use it, only for wifi passwords.
@low_cura
This is your Windows bug. I have Gigabyte Brix PC & Win 7, it has only usb 3.0 ports.
Mi Note 3, Moto E², Moto G³, Mi Pad 4, Nvidia K1 - all was flashed with fastboot.
On Mi Note 3 I can't disable Power Menu on lock screen.
Mi Pad 4(AICP), Moto E², G³ - I can disable/enable.
It is bug, as Quick Settings on Lock Screen at older builds.
Mi Note 3.
The power menu is available on the lock screen - despite the pin, fingerprint etc.
Developers options at the end: "High-risk feature is enabled" - what is this?
If you do not flash China Rom with MiFlash you will not know if the error is related to the software or the subassembly.
After checking you will return to Miui Eu.