Remove apple id

If you forgot the Apple ID (iCloud) password, enter the Apple (iCloud) ID, and click Forgot Password. See if you can get a Rescue or Notification email option if necessary. Link to contact Apple Support at the end of the 2nd article.

Apple ID - Manage

Apple ID – Forgot Password  *      

If you have 2 Factor Authentication enabled, if you can't recover the password using the steps above, you will need to use Account Recovery. The Recovery Process is an automated process and the length of time it takes can vary a lot. Apple ID Support can only answer your questions. They can't intervene in or speed up the process. The article below has some suggestions to shorten the time the process takes.

Apple ID - Recover your Apple ID with two-factor authentication account recovery.   *

If you have changed your password, have you followed the steps in this article on all devices/computers? 

What to do after you change your Apple ID or password - Apple Support.  *

Is the device you trying to use activation locked? If you cannot recover your old Apple ID and password and you have valid proof of purchase information you can start an activation lock request see this link for further reference

How to remove Activation Lock - Apple Support

If you want to delete your old Apple ID see this Link for reference How to delete your Apple ID account – Apple Support (UK)

You will need your Apple ID and password, you can try to retrieve that via iforgot.apple.com