Answer to Question 1
Automatic reinforcement means that a behavior produces its own reinforcement, without another person to deliver it. An example is scratching your skin. The act of scratching produces stimulation that may be reinforcing to an individual.
Answer to Question 2
Reinforcement is arbitrary in the sense that any behavior that is followed closely in time by a reinforcer gets reinforced. It does not matter if the behavior is desirable or not or whether the delivery of reinforcement was programmed/intentional or not. Behaviors are selected