Understanding Activation Lock
The easiest way to unlock your device that you’ve forgotten the Apple ID to is to take the device to an Apple Store along with proof of purchase and ID.



The iPad will definitely appear in the list of devices for the Apple ID that the iPad is asking for. If the device had been removed from the account, the iPad would no longer ask for that Apple ID as part of checking activation lock.

There is no way to identify the full email address the iPad is asking for. This would provide a means for a thief to conduct phishing for the owner's iCloud credentials.

The password asked for is the current iCloud password. You are performing the sign in over the network with Apple, requiring current credentials.

Incorrect password attempts may lock your Apple ID. The device will not become permanently locked through Apple ID login attempts.


  After multiple unsuccessful attempts to unlock your account, your Apple ID will remain locked and you can try again the next day.


https://support.apple.com/en-gb/HT204106