Here the case,

This Ipad Mini 1st gen bought by my aunt 3 years ago as my grandfather present. Most of the time the iPad play by the children of my family. one of the kid set a 4 digit pin code that use to unlock the screen and forgot the password.

After that, my family send the iPad to a mobile shop. The stupid shop do a factory reset to the iPad but still cannot unlock it coz of the activation lock.  The apple ID randomly register by my aunt 3 year ago, no one know the ID and password of the iPad.
my family finally found the resit last week(this ipad already brick more than 1 year）.
i already call to apple care seek for help. The CS say need to show prove of purchase and need about 5 working day to do verification.

but the shop that my aunt purchase the iPad is not an authorize apple store, it just a normal mobile phone shop at kuantan and only provide a handwritten resit.  I feel that the chance to get unlock is almost impossible.
anyone have similar experience to share with me ?
My advice for apple fans
1.Keep your resit, even your warranty already expired.
2.When buy 2nd hand apple product, make sure seller can provide resit.
3.set your apple id and password recovery properly.
4.Better buy from authorize apple store
all the way to unlock it as i know
1.have a resit, and apple care can reset the password for you
2.change a brand new motherboard.(expensive)
3.change the chip that store the apple ID(Cheaper but need touch the MB, might cause highly damage to electronic product)
4.some ppl provide unlock service, but is expensive and dont know how they do it.(never try no comment)
any progress i will update here