IPad Pro demo mode

If you are referring to the activation lock, there is nothing at all you can do. Only the original owner can do that. Return it and tell the gift giver that it is not usable unless they prepare it properly. If it is in demo mode, only a store would probably do this, so are you sure it is not stolen?

That is because you are not the person/store who set up the demo mode. There is nothing you can do except to return it or recycle it. I have never heard of anyone selling any device in demo mode; as I said, that is only installed by stores so customers can check it out, play with it, etc. A store would not sell it without returning the device to a usable condition.