A and C sound like barrier frustration and fear reaction, B is a transfer of that behavior (see above post for solutions). When did this behavior start (especially the barking at people entering the house)?
2 is the age of maturity for most breeds, which often means that this is when dogs become reactive to people or situations that bothered or terrified them as puppies. It also represents a progression. Instead of simply showing avoidance behaviors, they escalate and become pro-actively aggressive (because avoidance behavior did not stop the things that made them upset - they try harder to make them go away).
Your best solution is to change your dog's emotional response to the stimulus - when they are no longer afraid this will stop the barking.