Do I need to sign the back of calligraphy and painting for my friend?

1 must be added? Without signature, it is equal to a semi-finished product. 2. Just put your personal name stamp at the space between words under your name. If there is an introduction chapter, it should be stamped between the first and second words on the right side of the calligraphy content. Be careful that the name stamp is not bigger than the word. The main function of the seal is to fill in the blank? Ask for an article