I'm not really sure if there is a certain exercise that allows you to loose only chin fat. However, if you just start exercising in general, i can guarantee that you will loose chin fat, and other...
Sure. If someone who hasn't been working out before should suddenly start training fairly hard, then they can gain muscle mass at pretty much the same rate as they are losing weight as fat.
You really shouldn't try for a fast weight loss. What's put the weight on is a long period of poor lifestyle choices, and what'll give you the best shot at not only getting the weight off but also...