What suddenly becomes your third foot, a faithful support that appears when your own legs begin to falter?

I eat you alive, yet you feed me willingly every day. Solve the riddle → Many stand in line for me, but I have no legs. I can grow long, yet still be invisible. Solve the riddle → More than twelve eyes witnessed the event, yet only two people were present; how is this possible? Solve the riddle → I'm unique: You throw away my outside to cook my inside. Then you eat my outside and throw away my inside. Solve the riddle → Our internal purification plant quietly filters toxins without asking for a raise. Solve the riddle →