Answer:
What can be filled with empty hands?
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.
I am black when I am clean and white when I am dirty?
I have a hundred legs, but cannot stand. I have a long neck, but no head. I cannot see. I'm neat and tidy as can be.
You should keep it as straight as can be, yet very few do. Most of the time it's slightly bent or curved. Your sadness usually causes it to bend further, but don’t bend it for too long or it may never be able to fully straighten out again. What is it?
If it’s information you seek, come and see me. If it’s pairs of letters you need, I have consecutively three. What am I?