The security questions are associated with your Apple ID account. Security question answers are not case sensitive, but if you have forgotten them see this Apple support article—>About Apple ID security questions - Apple Support
This may also help—>If you forgot the answers to your Apple ID security questions - Apple Support
If you still can’t get in to your account you need to contact Apple’s security team—>Contact Apple for help with Apple ID account security - Apple Support
They will need to verify that you are who you say you are, and not a hacker trying to gain access to your account. As most of your “private” information is now available on the dark web (Thank you Equifax!) this can be quite difficult; asking you something that would not be generally known that both you and Apple know.
Note that if you enable 2 factor authentication on your Apple ID account you no longer need (or have) security questions. See—>Two-factor authentication for Apple ID - Apple Support