@davidfrei7as & @Jake Lo, Thanks, I was able to use David's EFI and perform an uprade from BigSur to Monterey. Overall it was a smooth process but for below few issues.
Wi-Fi did not work in Monterey, which was working in BigSur. Fixed it by applying the latest stable airportitlwm.kext (which was not available in David's EFI)
Bluetooth is not working in Monterey, which was working fine in BigSur. I don't remember applying any kext for bluetooth in BigSur, not sure what is missing now?
System Preference is laggy in Montery (particularly Trackpad & Bluetooth settings are not opening). Any inputs?