Answer:
I am so simple that I can only point. Yet I guide men all over the world.
There is one word that stands the test of time and holds fast to the center of everything. Though everyone will try at least once in their life to move around this word, but in fact, unknowingly, they use it every moment of the day. Young or old, awake or in sleep, human or animal, this word stands fast. It belongs to everyone, to all living things, but no one can master it. The word is?
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.
It's equally comfortable in an orchestra and a geometry textbook. What is it?
What is it that given one, you’ll have either two or none?
I have two eyes in the front and a lot of eyes on my tail