Answer:
I am commonly abbreviated to H
Squeeze me and I cry tears as red as flesh, but my heart is made of stone. What am I?
Without a bridle, or a saddle, across a thing I ride a-straddle. And those I ride, by help of me, though almost blind, are made to see. What am I?
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. What am I?
What has legs but doesn't walk?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?