mishtia005 It wouldn't be that difficult for somebody to build a custom version of GrapheneOS that won't enter Recovery and won't enable developer mode. I can't speculate about why somebody might have done that, but if they sold the phone to you that way then it was sold in a defective state. Perhaps you can return it?
I don't know this for sure, but I think there is some reason to believe that Google repair centers have a way to forcibly re-flash a device in this state. You might try asking a repair shop what they think.