What Am I Riddles

Question: sometimes i hang, sometimes im crusty, sometimes im bloody, and yellow. What am i?

Question: What lightens the light and darkens the dark?

Question: I always listen to my Master, I never disobey. From my path I never stray to destroy what's in my way. What am I?

Question: I'm in every room, yet outside. I move at different paces, but you never see me moving. Where ever I am its crowded, but when your there you don't see or feel anyone. If you try to hit me you always miss, yet you always feel me. You need me to live, but I cause disasters. What am I?

Question: What force and strength cannot get through, I with a gentle touch can do, And many in the street would stand, Were I not a friend at hand.