The people in this community are customers like you can can only provide advice, not actually do anything about your account.
In 2015 Apple transitioned to using two factor authentication instead of security questions.Since then Apple has been persistently encouraging users to switch to the more secure system. Apple allows you continue to use security questions if you already use them, but if you end up having problems then they no longer get direct support.
You can try the reset service at this link ➞ https://getsupport.apple.com/?caller=cups&PGF=PGF63005
Select “Forgot Security Questions” then “Continue”
Additional reset methods are provided in this support article https://support.apple.com/HT201485 but the article is labeled "archived" and may contain information that no longer applies.
If resetting works then fine, but if it does not (e.g., you see “not enough information”*) then you will have no option but to change to the newer security method, if you can. For those who have disregarded Apple’s encouraging to change to two factor, Apple will likely only help you to now change to two factor authentication, if even that is possible. Follow the instructions in the "Turn on two-factor authentication for your Apple ID" section in this support article --> https://support.apple.com/HT204915 to try to change to two factor authentication.
If you still need help, contact Apple Account support If that does not work you can contact Apple support and service; click here ➔ https://support.apple.com/106932
If Apple cannot, or will not, help you transition to two factor authentication then it is quite possible you will have to simply abandon the old account and everything it contained. In that case, if you were using the Find My service, the Activation Lock support request support article at: - https://al-support.apple.com/#/additional-support may at least let you regain use of your equipment. If not, you will also have to say goodbye to the device as well.
Good luck!
*More about identity verification problems here —> https://discussions.apple.com/thread/256247991?sortBy=oldest_first
