Watermarks are a great way to protect your photographs if you don't want other people misusing them. We will create a simple but effective text and turn into a Gimp brush so you will be able to stamp your work.
If any file can not be deleted, then you can use the program LockHunter, which removes the active connections of other applications to that file, which allow you to change or delete file.
At any given time you can reset your Nexus 4 smartphone to the factory default settings, meaning you will bring your phone back to the same state as it was on a day when you took it out of the box.