After not being able to downgrade I tried many ways like downloading various version of iOS firmware compitable with my iPad and tried downgrading it but nothing good happened. But at last I finally found the solution. That is...
Note that you don't need to download any firmware.
Step 1: Create another icloud ID for free but don't register these ID in Apple developer website.
Step 2: Deauthorise your iTunes with the Apple ID that you have registered to apple developer.
Step 3: Now connect your apple device by putting it into Recovery Mode.
Step 4: Restore your device but when iTunes ask you to input password for your Apple ID just type the new Apple ID that you have created and proceed forward you are done now.....ENJOY!