Answer:
I have two bodies joined together as one. When standing still I run and run.
What word has kst in the middle, in the beginning, and at the end?
I have a head and a tail but my eyes can never see my tail.
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.
You throw me out when you use me and take me in when you are done.
Lynn likes grapes but not potatoes. She likes squash but not lettuce, and she likes peas but not onions. Following the same rule, will she like pumpkins or apples?