How to Unlock Redmi Note 7 Bootloader
To unlock Redmi Note 7 bootloader,
Download Mi Unlock Tool.
Sign-in with your Mi Account on your device.
Go to Settings > About Phone > MIUI version and MIUI Version 7 Times.
Now go to Settings > Additional Settings > Developer Options and check “OEM unlocking” [this should be already checked] and “USB debugging.”
Turn off your device.
Press and hold Volume Down + Power button until you see the Fastboot screen.
Connect your device to PC.
Run Mi Unlock Tool.
Sign-in with your Mi account.
Start the unlock process.
Read on-screen instructions.
Reboot your device.