Unable to recover stolen Apple ID account and unlock Mac

Our family member had their Apple ID stolen 6 months ago. They didn’t notice the email from Apple about removal of phone number and changed the secure device. Apple gives a week for you to revert the changes if your account got hacked which we missed that deadline as presented in the same email. At the moment, Mac that has the Apple ID is locked and can be regained access by presenting the purchase bill. Phone number in the account changed multiple times that we no longer can recover the account.

We still have access to the original phone number (the phone number that used the create the account) and the email address. The hacker did not change the email address. Only phone number, password and secure device were changed. We want to again access to the account or at least the email to be removed from that account. Email address’s name is the full name of the owner. We could provide legal ID and passport to verify the ownership of the email as well as we have access to inbox of that email.

Is there a way to contact someone from account security to reclaim the account or at least the email to be removed from that account? We have called Apple Support in our country, they can only help with the unlocking of the devices.