Two-factor authentication for Apple ID - Apple Support
"With two-factor authentication, you don't need to remember any security questions. We verify your identity exclusively using your password and verification codes sent to your trusted devices and phone numbers. When you enroll in two-factor authentication, we keep your old security questions on file for two weeks in case you need to return your account to its previous security settings. After that, they're deleted."
To see how to 'Get a verification code and sign in with two-factor authentication', click here --> https://support.apple.com/HT204974 - "Whenever you sign in with your Apple ID on a new device or browser, you'll confirm your identity with your password plus a six-digit verification code. There are a few ways you can get a verification code. You can use the code displayed on your trusted device, get a text or phone call, or generate a code from your trusted device." Instructions at the end about what to do if you don't have any other trusted devices and need to use account recovery.