I cannot remember the 4 number identifier. I am trying to erase my old Iphone 7 of all information, photos and documents. I go to setting, General and Erase all. Then it ask for my Apple user name and password. I enter each as was created the day I purchased the Iphone 7 (never changed it) and I have it written down in my wallet. I enter those items and the system says, ID and password DO NOT MATCH! What a crock! This is worse than trying to do brain surgery. It should be simple, but the system has made it so darn difficult to get done. I am stuck here with two phones. A new Iphone 11 and an old Iphone 7. I wanted to give the Iphone 7 to my granddaughter to use for gaming. I cannot give it to anyone until the system is erased. I need someone's help?