iPad: Basic troubleshooting
Update and restore alert messages on iPhone, iPad, and iPod touch
iOS: Resolving update and restore alert messages
iPad: Unable to update or restore
iTunes: Specific update-and-restore error messages and advanced troubleshooting
I had the same issue with my ipad4. It was working fine until 9.0. then apps would fail, Then 9.01 and it was worse, then when 9.02 came out none of my apps worked.
I followed instructions and was getting 4015 errors. I took it to the Apple store and they tried reloading and now get 4005 errors. They say it is hardware and I cannot load any os to my ipad.
I have seen the blogs. Tons of people are having the same issue with older ipads. What can we do but ofc buy a new one.
Sadly it is time tell Apple good bye.
RIP Ipad, I loved it but thanks to os upgrades it is history!!!