How to completely erase my iPad but leave one app?

So, I cracked the screen on my iPad. It sucks, I know. It still works fine, but I wanted to replace it and it was cheaper to buy a used one in good shape then replace the screen.

I think I can recoup my losses, because it has flappy bird on it. I still see iPads going for a lot on ebay that have it, so that is my plan. However, for security reasons I want my account to be detached from the iPad. And I will delete everything else so it is as close to factory fresh as possible. I do, of course, want to leave flappy bird. Essentially, I want to make my ipad completely new except with flappy bird app. Is this possible?

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