Dear,
NO ONE knows whether the Tablet is working or not unless they open the seal and check by themselves.
Once opened, Buyers do not buy that piece as it was not sealed pack.
That is why there is manufacturing warranty where we all need to go in person to fix the problems.
I purchased Galaxy Tab some where in Samsung retail store and i got a problem, when i went to that store again by asking to fix the problem, they suggested me to send the phone to service center.
This is how it works. It is not only in our country but every where.
IF THE SELLER DESCRIBES AS MANUFACTURING WARRANTY THERE IS NOTHING THAT SELLER CAN DO, BUT ASK YOU TO GO TO TO MANUFACTURER.
IF SELLER DESCRIBES AS DEALER WARRANTY , THEN IT IS SELLER RESPONSIBILITY TO FIX IT.
I hope you understood what i said.
thank you