Hi, I am not quite sure I understand. If you have a picture with an attached common event, it will run the common event every time you click the picture by default, it doesn't only run once and then need to be re-attached.
As far as I am aware, pictures are layered in the order they are created (Picture #5 appears above Picture #4). This is default RPG Maker MZ behavior, and [CGMZ] does not change that. If you are not seeing that behavior, you may have another plugin that affects how pictures are drawn.