4 ways of using it come to my mind:

• Place hands on the inclined outer handles and do a pull up with arms open wide
• Place hands with palms facing the wall on the "inner" handles and do a pull up with arms at shoulder width
• Place hands with palms facing my face on the "inner" handles and do a chin up
• Place hand on the handles which point out of the wall and do a pull up / chin up (sorry don't know in this case)

Are these excercises different for the group of muscles they target? And if so, how? Is there any ranking among them from worse to better?

Also if I can do chin ups just fine but I can only do negative pull ups, which ones should I choose?