1) No problem. This is a very normal set up. It is allowed to put 15 amp receptacles on 20 amp breakers. The wiring undoubtedly is 12 guage, adequate for the 20 amp breaker. The idea is that it is not necessary for each individual receptacle to be 20 amp rated, as very few devices found in the home require that. But by making it a 20 amp circuit, you are less likely to run into trouble when a lot of items.....computer....etc.etc. are plugged in the same room/
2) Not sure about that.....waiting for input from others.