Click on this link to read what to do "If you forgot your Apple ID [Account] password" --> https://support.apple.com/HT201487
or go directly to this link --> http://iforgot.apple.com/
Also read about "What to do after [or before] you change your Apple ID email address or password" --> https://support.apple.com/HT204071
If you didn't receive your verification or reset email, click here --> https://support.apple.com/HT201455
If you are being sent a verification code to a phone number to which you no longer have access, click on the next link to see the various ways of getting a verification code and what to do if you cannot get one:
Get a verification code and sign in with two-factor authentication --> https://support.apple.com/HT204974 and a related new feature: Account Recovery Contact --> https://support.apple.com/HT212513
If you still need help:
Contact Apple for help with Apple ID account security "This article provides country-specific Apple Support contact information for customers seeking help with their Apple ID password or other security-related issues." --> https://support.apple.com/HT204169
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About Apple ID security questions
Click here --> https://support.apple.com/HT201363 to "Learn about Apple ID security questions, including how to set up or change your questions."
"If you forgot the answers to your Apple ID security questions" click here --> https://support.apple.com/HT201485
If you see the message "not sufficient information" see if at this stage you can still sign up for Two Factor Authentication. Apple has been very strongly urging users to use Two Factor Authentication instead of security questions. "With two-factor authentication, you don't need to remember any security questions.
Click on this link for more information about 'Two-factor authentication for Apple ID' --> https://support.apple.com/HT204915
If you cannot resolve the issue by signing up for Two Factor Authentication, "Contact Apple for help with Apple ID account security"; click here --> https://support.apple.com/HT204169
