Q: This Apple ID has been locked for security reasons

Apr. 2016 King_Penguin post: https://discussions.apple.com/message/30030420#30030420

If your Apple ID is locked - https://support.apple.com/HT204106 - "If you or someone else enters your password, security questions, or other account information incorrectly too many times, your Apple ID automatically locks to protect your security and you can't sign in to any Apple services. You can unlock your Apple ID after you verify your identity."

Write down the answers to your security questions.  They are like knowing you bank account information.

Normally you can't use an iCloud address as the contact e-mail. You probably used a different one.

If none of those work you will have to contact Apple using the information in the articles I linked.

If you can't unlock the account yourself then contact Support in your country : Contact Apple for help with Apple ID account security - Apple Support