The software is called XiaomiTool v2 and can be downloaded to your PC from here https://www.xiaomitool.com/V2/download

All you need is a Xiaomi phone with usb debugging enabled.
A good USB cord, strong/fast internet access, after installing and launching the software, connect your phone to your PC, wait for the software to recognise your phone then select it.

It's pretty self explanatory and easy to use. I was able to download and install the official recovery ROM for my phone, despite the restriction placed on my phone by Xiaomi. I was able to download the latest recovery ROM through the software, and it automatically installed it (sideload). This took less than an hour to complete.

Now I have upgraded my redmi note 11 to android 12.

Please note that this method is risky, so you need to backup all your data to a separate external storage to avoid loss of your important data, before you start the process of upgrading. Also make sure the USB cord is good and stable, if you mistakenly disconnect your phone during the upgrade, this would brick your phone. So make sure you place your PC and phone where it won't be disturbed, and be very patient while it's upgrading.