Answer:
Curtail me thrice I am a youth; behead me once a snake; complete I'm often used in truth when certain steps you'd take.
I turn everything around, but I cannot move. When you see me, you see you! What am I?
I widen my jaws when you poke two fingers in me. I especially like to devour papers
I'm tall when I'm young and I'm short when I'm old. What am I?
I have a head tail but no arms and legs.
The answer I give is yes, but what I mean is no. What was the question?