For the first question, see my response in the other thread you created. For the second, you can add custom stamps by tapping the stamp tool icon in the annotations editor twice to show the stamps window, tap the User category, tap the + icon and then you can add any of your own custom stamps. I've attached some stamps from another user in case they are helpful for you. One thing I will say is that these are image files, which do not scale well. If a .svg file were used instead, it would scale to any size without a loss in quality, so that's generally a better approach to use.
Mike
Mike