( YOU SHOULD KNOW  WHAT YOUR DOING)-
Note - make sure u have adb driver install
After binding account you need to  wait 7 days (168h) to unlock 
Make sure u don't logout, Remove sim,reset etc after binding account
Your mi account must have a phone number linked to avoid verification issue
Use official mi unlock tool
Unlock bootloder will do a factory reset so make sure you Backup your data
Step 1: Enable ‘OEM Unlocking’ on your phone
Go to ‘Settings‘ > ‘About phone‘ on your Poco M2 pro.
Continuously tap on the ‘MIUI version‘ section for five (5) times to enable the hidden ‘Developer options’.
•Now, go to ‘Settings‘ > ‘Additional settings‘ > ‘Developer options‘.
•Find ‘OEM unlocking‘ and turn on the toggle next to it.
•Tap on ‘Enable‘ when prompted to finally enable OEM Unlocking on your Poco M2 pro.

Step 2: Bind your Mi Account to your Poco M2 pro ( MAKE SURE UR MI ACCOUNT HAVE PHONE NUMBER LINKED)
•Go to ‘Settings‘ > ‘Additional settings‘ > ‘Developer options‘ on your Poco M2 pro. 
•Goto unlock status tap on ‘Add account and device‘ and log in to your device with your Mi account.

Step 3: Unlock the Bootloader on your Poco M2 pro
•First, power off your Poco M2 pro completely and boot into fastboot mode
•Connect your phone to the PC while it’s in Fastboot mode.
•Open Mi Unlock tool and Log into your Mi account in the tool’s GUI.
•The tool will now verify your phone to check if it’s eligible for bootloader unlocking.
•Upon successful verification, the tool should show ‘Phone connected‘.
•Now click on ‘Unlock‘. The tool will prompt you with a confirmation message.
•Finally, click on ‘Unlock anyway‘ to confirm and unlock the bootloader on your Poco M2 pro.