Here are additional methods you ... Apple ID if you don't recall the answers to your security questions: Use Account Recovery: If you can't access your recovery email or don't have two-factor authentication enabled, you can initiate an account recovery. This process may take several days, but it allows you to regain access without needing the security questions. Start the process by going to iforgot.appl... More on discussions.apple.com

I rely on this Apple ID for daily use, and losing access is causing significant disruption. Here is a summary of my account and recovery attempts: ... • Recovery attempts: Attempted password reset via https://iforgot.apple.com, but could not complete verification without the trusted phone number More on reddit.com

https://al-support.apple.com/ More on reddit.com

Your post is rambling so I can’t figure it out. Just to cut to the gist - Nothing can restore access to the phone. Not Apple. No one. Once a phone is locked it’s locked forever. The only thing that you can do is erase it and start fresh. At that point you’d use a backup to restore the phone to its usable state. A backup is on iCloud or a computer that was connected to the phone. No backup? That’s it. All data is gone forever. You’d have to start over with a blank iPhone. All the stuff you wrote about is so that you can gain access to your sister’s Apple Account. This is required to erase the iPhone and start the process I described. You said “she kept all important data and backups on the same device”. If that means she never turned on iCloud backup or connected the phone to a computer to backup then that was a huge mistake and all her data is gone. More on reddit.com