This is the correct procedure to prepare a device for reuse - that will prevent issues with Activation Lock:
https://support.apple.com/en-gb/HT201351
If you didn’t follow the defined process, I fear the boat has already sailed.
Here is a procedure to attempt recovery of your AppleID and associated password. This portal is where you start:
https://iforgot.apple.com
AppleID credentials don’t “evaporate”; as such, unless the account is frozen or otherwise totally disabled, you should be able to recover the original AppleID that secures the Activation Lock.
To recover your credentials, you’ll need access to one of the following:
- Your primary email address mailbox that corresponds with your AppleID
- Any of the secondary/recovery email addresses that should be configured for your AppleID account
- Any of the trusted telephone numbers (fixed line or Cellular/Mobile) that are associated with your AppleID
Unless you AppleID account has not been fully/correctly configured, or has been seriously neglected, recovery of the AppleID and password should not be difficult.
More information about recovery of your AppleID:
https://support.apple.com/en-us/HT201354
More information about recovery of your AppleID password:
https://support.apple.com/en-us/HT201487
When you recover access to your credentials, you would be well advised to log-in to your AppleID account from a web browser - and verify/update any email addresses and trusted telephone numbers:
https://appleid.apple.com
If you cannot recover the AppleID - which, to be clear, is your greatest chance of success - your only remaining option is to seek assistance directly from Apple. Apple will require the original sales invoice that clearly shows the serial number of the device; if acceptable documentation is not available, Apple will not assist - the game ends and your device remains forever locked.
I hope this information proves to be helpful in either resolving the problem - or at the very least making clear the limit of your options.
