Q: locked ipad

dears,

I have my daughter's ipad mini set up about 4 yrs ago and its locked now (disables for security reasons) due to mistakenly password entered by my little daughter. I have registered then the ID, password, birthdate (her mother's one) and the security question's answer, however I cant access the email to recover the password as the icloud account locked. also the security question's answer is not correct as it says!! I don't know why.

I have called apple center to have a solution but couldn't, since the both ways are not working with me, they have asked about the invoice of purchasing but I don't have, as I bought it long time ago and from another country from where I reside now.

I asked them if there is any other way to prove that this device is ours, but no use.

this is really frustrated. the device ipad mini is old but good condition & my daughter is using it frequently and now its locked, should I through it in the garbage because of that!, knowing that no account ever used on this ipad but her's, and I have the password and the ID correct.

anyone can help what to do.  many thanks.

note: I promised myself if I could not solve this ipad's problem, I will never in my life buy another apple product!!