Q: i will reset all contents

Okay good luck with that.

Okay, go ahead.  Not sure why you want to do that, but you don't need our permission.

Well, I wouldn't open up your phone because that will void the warranty.

I don't know.  What is the permission?  You're telling us you're going to reset the contents of your iPhone.  Okay, fine.  Go ahead and do that.  You haven't told us why you want to do that, or what problems you're having. No one here can make you do anything or keep you from doing anything.

Why do you want to reset the contents of your phone?

If you've purchased a second hand iPhone, and the device is requesting that you enter in the Apple ID and password that was used to enable Activation Lock, then you'll need to contact the seller and have them do that for you.  No one here can help you.

Find My iPhone Activation Lock: Removing a device from a previous ...