No, the body and mind are two separate entities, however they do go hand in hand. But because you are physically fit it does not mean you are mentally fit.
I reckon it does. Wii fit has a range of muscle workouts and aerobic excersises to burn fat. It stretches many muscles, and is very accurate. However, if you are still a child, it may not mark you...
A lot of stuff that really ain't worth it. It costs money and resources, and it takes away a lot of freedoms, and as soon as school is over, there is no "fitting in" so it's really most often a waste...