Most experts believe that 3-5 times per week for duration of 20-60 minutes at 60-90% of age-specific

Actually, you're almost always burning fat at one rate or another, but you burn most when your body is in its aerobic range. A good rule of thumb is that after 20 minutes in your aerobic zone, you will be burning more fat than carbos. Experts states that you will be burning fat after only twelve minutes of aerobic exercise. If you can increase your aerobic activity to 30 minutes or longer, you will be burning a larger percentage of calories from fat. There is still some disagreement as to which is better - longer duration at lower intensity, or shorter duration at higher intensity. If you are limited in time, then the higher intensity will maximize your aerobic benefits in a shorter amount of time. If you can work for a longer duration at a lower intensity, you will decrease your chance of injury. The object is to burn more calories than you take in. 3,500 calories equals l pound of fat. Your muscles will continue to burn fat after both aerobic and anaerobic (muscle training) exercise.

No. When we're working a muscle or group of muscles to burn fat, we have no control over what part of the body we burn fat from. There is no such thing as "spot reducing". Fat generally is used up in pretty much the reverse order it was put on, when you are exercising; the blood is carrying fat from all over the body to provide the energy. The muscles which are being worked will improve, of course, so when the layers of fat finally do get worked off, you'll have some nice lean tissue to show for all your efforts.
Another aspect to this question is the fact that muscle growth underneath a fat deposit can give the appearance of spot reduction. This is because the overlying fat is stretched over a greater surface and appears thinner, although the total amount of fat is the same. A good analogy is with a balloon. As the air is increased, the skin on the balloon gets thinner, but the amount of balloon material stays the same. I think that this may be how the spot reduction myth originated. By working the muscles below the fat, people think they are actually making the fat go away.

It is a good idea to start slowly and build up to a full program. Walking is the easiest way to begin a program. Start with a stroll for a mile or so and build up to walking 3-4 miles per hour. As you become proficient at walking, you might want to try another activity such as jogging, running or even aerobic or step classes. The best aerobic program is the one you enjoy and will stick to. Remember, the journey of 1000 miles begins with but a single step.

If you feel like eating immediately after a workout, be sure that it's high in carbohydrates, lower in protein, and either very low or no fat content. The carbs should be mostly complex. Durum or semolina pasta, fat-free granola bars, and some of the lower-sugar fig or other fruit bars are fine. Try to take in as few kCals as you can - just take the "edge" off. Munching out on broccoli or cauliflower florets with just a touch of fat-free Ranch is good.
If the workout was pretty intense, I'd recommend about an hour's wait afterward before eating a full meal. Most people aren't really ready to eat when they're majorly sweaty and still breathing heavily, anyhow. Cool down, then grab a nice refreshing shower, and mellow out with a big glass of ice water. Next, find some candles, and sit down to a nice plate of rigatoni with tomato sauce with basil, green peppers, and little bits of chopped mushroom. Brush your whole wheat toast with a film of olive oil, sprinkle on some freshly-chopped garlic, you get the picture.

Consider that you will probably burn between 300 and 450 kCal in an aerobics class. Keep the caloric content of the meal below that if you're intending to lose weight. That pretty much lets out any sort of "heavy" meal. The average American's diet is very high in protein, and relatively low in complex carbohydrates, so complex carbs before an aerobic workout are probably better. Keep the total calories from fat to 25% or lower, in general.