im completing my apple id, but it keeps asking for year of birth. There's no option to write it anywhere.

This is the exact same thing as in this question from 2017: https://discussions.apple.com/thread/8024437

(Using the iTunes interface, under Complete your Apple ID, on the page where there is the payment method and billing address, I keep getting the error message "Enter your year of birth." There is no form field for this in iTunes.)

However, following the advice from there, which says go to Update the birth date associated with your Apple ID, I sign into https://appleid.apple.com/ with my username and password, then get a screen that reads "Verify your email address". When I enter the email address that is my Apple ID, I get the error "This email address is not available. Choose a different address."

This is my email address.

This is my Apple ID.

[Edited by Moderator]