Unknown Apple ID security questions for personal email

Hello. I was wanting to change my Apple ID email to my main personal email from my alt email, but when I tried to add my email in Apple ID means it’s invalid and someone took it already! I never even created any Apple ID associated with my email! But then I decided to reset password and success! I did reset my password successfully with my email. But when I tried to log in I hit another problem: security questions. I never knew or set them! I tried contacting customer support for over 3 times and unfortunately, they said that they can’t just reset the security questions without you knowing which are the answers. So I tried logging into iCloud and I did get into iCloud but they were empty like no one ever used it. That’s not what I’m concerned I’m concerned about the security questions because something or someone used my main email to setup their Apple account I never knew it. I tried resetting the security questions via iforgot.apple.com but it prompted me to answer these security questions so I can reset them which I never know what are they. Do you have anything that could work? Thanks!

[Re-Titled by Moderator]

Original Title: Apple ID Email Taken