Answer:
I have three feet but no arms or legs
Use me if you really want to see inside someone
I have no bed to sleep and no palace to live. I don't have a single coin but I am known as king. What am I?
I'm an animal. I love marching. I always wear a tuxedo. What am I?
I have no voice but I can teach you all there is to know. I have spines and hinges but I am not a door. Once I’ve told you all I cannot tell you more.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.