iPad: Forgot (Third-party email) Apple ID's password
One of my parents forgot the Apple ID password on their iPad, which they used a third party email (gmail) to sign.
Now, this gmail is not even accessible anymore (username cannot be found on sign-in page nor cannot be created on Google Accounts page).
They only remember the 6-digit Passcode, so they can still use their iPad in a daily basis.
However, it often prompts a small window asking for the password, which this email is not even working, so let's say... it's unrecoverable.
I was wondering if there's a solution for this account problem.
Thanks in advance.