Answer:
What word has kst in the middle, in the beginning, and at the end?
What is the heart of many risks, has a heart, but is not a living being?
Who spends the day at the window, goes to the table for meals. And hides at night?
You saw me where I never was and where I could not be. And yet within that very place, my face you often see.
Different lights do make me strange, thus into different sizes I will change.
I have two bodies joined together as one. When standing still I run and run.