iPhone 12 locked after passcode issue during transfer to iPhone 15 Pro Max

Hello Apple Support Community,

I would appreciate your advice regarding an issue I experienced while transferring data from my iPhone 12 to my new iPhone 15 Pro Max.

During the transfer process, I was asked to enter the passcode of my old iPhone 12. Although I entered what I believe was the correct passcode, it was repeatedly rejected. After several attempts, my iPhone 12 became locked and displayed the message "iPhone Unavailable."

I contacted Apple Support to understand my recovery options. I was informed that resetting the device would be necessary, which could result in the permanent loss of my personal data, including important photos and memories, because I do not have a backup.

Before taking that step, I would like to explore whether any alternative solutions are available.

I would particularly appreciate guidance on the following questions:

1. Has anyone experienced a similar passcode issue during an iPhone-to-iPhone data transfer?
2. Could this situation be related to a software issue during the transfer process, or is there another possible explanation?
3. Are there any official Apple troubleshooting procedures that could help restore access to my iPhone 12 without erasing its data?
4. Is there any way to verify whether the photos and other personal data can still be recovered before performing a factory reset?
5. Would contacting a different level of Apple Support or visiting an Apple Store provide any additional troubleshooting options?

I understand that Apple's security measures are designed to protect users' personal information, and I fully appreciate their importance. However, I would like to make sure I have explored all available recovery options before taking an irreversible step.

My main goal is to regain access to my device, or at least preserve my personal data, without compromising its security.

I would be very grateful for any technical advice, official Apple documentation, or experiences from community members who have encountered a similar situation.

Thank you for your time and assistance.