Answer:
I am flora, not fauna. I am foliage, not trees. I am shrubbery, not grass. What am I?
I have feathers that help me fly; with head and body but I'm not alive. Very skinny and a fixed length how far I go depends on your strength.
I have no voice but I can teach you all there is to know. I have spines and hinges but I am not a door. Once I’ve told you all I cannot tell you more.
I am filled with garb the price is free. Just return what you don't need.
I can be entertaining until you realize some pieces have been lost.
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.