I was wondering if it's possible to restore an android default settings without deleting any data or apps? It's because I buy android tablets then I install my app on it then I sell it back to a customer but I want it to go back when it came out of the box to ask for settings again once the customer turns on the device?
Restoring factory defaults without deleting any apps or data is a contradiction in terms, as that's exactly what the reset does (see: factory-reset).
Could it be you just want your app to survive, but don't care about everything else being reset? That could be done by making the app a system app (see: system-apps), which requires the device to be rooted (see: rooting, root) in the first place.
Apart from that, the answer is "No". As soon as your customer applies a factory-reset, your app will be removed as well.