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See If you forgot your Apple ID https://support.apple.com/en-us/HT201354

And, see If you forgot your Apple ID password https://support.apple.com/en-us/HT201487

You also can use Having trouble signing in/iForgot https://iforgot.apple.com/password/verify/appleid to try to recover it.

And you may need to see If you forgot the answers to your Apple ID security questions https://support.apple.com/en-us/HT201485

Before trying to answer your security questions is very important that you think about your questions, including your birth date, and their answers carefully and try to recall all details you can. If you don't answer them correctly enough, then you easily can lose control of your account.

Note that If you're using two-factor authentication and can’t recover your password, you usually will need to enter account recovery. See Recover your Apple ID when you can’t reset your password  https://support.apple.com/en-us/HT20492

And, in general, if things go badly using the above links, you will need to try to recover your account if you want to use it again. Again, see Recover your Apple ID when you can’t reset your password https://support.apple.com/en-us/HT204921 Use the link to request account recovery to regain access to your account.

If necessary, If you are the original owner, contact Apple. Apple can remove the Activation Lock if provided the required paperwork. Either take the device, the original purchase receipt with the serial number, and a photo ID to the nearest Apple Store (if it has reopened)

Genius Bar Reservation and Apple Support Options - Apple.    

or contact Apple ID Support. 

 Apple ID - Official Apple Support.    

Contact Apple for help with Apple ID account security - Apple Support.  (Link doesn’t always load)   

Get Support      Work through the screens to get a chat option. 

Apple Support schedule phone call

https://twitter.com/AppleSupport       People have posted it may take an hour or more to get a response.