How to retrieve photos from an old iCloud account without 2-factor authentication?

Based on: Get a verification code and sign in with two-factor authentication - Apple Support

A code is sent first to your trusted devices (some other Apple computer or Apple mobile device signed in with your account) automatically. If you have a trusted device running iOS 9 and later, OS X El Capitan and later, iPadOS 13 and later, or watchOS 6 and later, the verification code is displayed automatically on your trusted devices.

It is a good idea to have more than one trusted number.

If you had set up a recovery contact, read Help a friend or family member as their account recovery contact - Apple Support

If you can’t sign in, reset your password, or receive verification codes, you can request account recovery to regain access to your account [ How to use account recovery when you can’t reset your Apple Account password - Apple Support ]. Account recovery might take a few days or longer, depending on the specific account information you can provide to verify your identity.

I see you are already working with Apple about this. Realize that they have no way of telling that you are not some scammer trying to trick his way into another person's account. Modern day security works both ways and ultimately you will have to prove to them you know things about the account that only the true owner would know. If you cannot prove that using Apple's criteria then you will not have access to the account.

See How to use account recovery when you can’t reset your Apple Account password - Apple Support