How to change answers to security questions

Reset them in your Apple ID Account https://appleid.apple.com/#!&page=signin if you can. If you can't sign in, then you would have, or will be unable to, answer your security questions satisfactorily. 

So, see If you forgot the answers to your Apple ID security questions https://support.apple.com/en-us/HT201485

Since you would be, or have been, unable to answer your security questions satisfactorily see Security and your Apple ID https://support.apple.com/en-us/HT201303

 This document says “without proof of your identity via security questions and other carefully selected criteria, Apple Support can't help you reset a password or perform any other actions on your account.”

Thus, we can do nothing to help you, except to mention that Apple support might help you if you have an extenuating circumstance (e.g., you have your receipt for your purchase of a pertinent device from an authorized Apple seller with its serial number on it). If you want to contact Apple Support to discuss any possible extenuating

circumstance, see the support options below. Alternatively, if an Apple Store is open in your area, then you can go there to deal with your extenuating circumstance. You also can make a genius-bar appointment (https://www.apple.com/retail/geniusbar/) if you want.

Get a call from Apple support to help solve your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362

Apple ID Support https://support.apple.com/apple-id

Apple Support Twitter  https://twitter.com/AppleSupport. There may be a wait.

Apple ID account security for country-specific and region-specific help https://support.apple.com/en-us/HT204169

Get Support: We’re here to help https://getsupport.apple.com/. Go through the options to find the best support option.

Reset Security Questions

Contact Apple for help with Apple ID account security

If you forgot the answers to your Apple ID security questions - Apple Support

You may need to reach Apple’s Account Security department. If you cannot find your country or are not able to call, then complete this form and send it to them.

Try using Apple's iForgot service. If it says they don't have sufficient information, you need to contact Apple's Account Security team. To reach them, click here and pick a method; if you can't use any of the ones listed, fill out and submit this form.

For Problems With Your Apple ID

1. Forgot iCloud Password
2. Forgot Apple ID
3. iForgot Password - Apple ID
4. iForgot UserName - Apple ID
5. Apple ID Password Change
6. Apple ID Name Change
7. Apple ID - Apple Support
8. Manage your Apple ID primary, rescue, alternate, and notification email addresses
9. About your Apple ID email addresses
10. Get help with Apple ID
11. Contact Apple for help with Apple ID account security - Apple Support
12. What to do after you change your Apple ID email address or password - Apple Support