Best exercise to loose belly fat quickley ?

Hiking. It mixes up the walking with some strengthening. Pick a good uphill slope with large rocks if you can find one. This way you are walking uphill and using arm and stomach muscles to pull up and manuever around rocks. Hope that made sense ...
Do not do curl ups! Not until you have lost most of the fat first anyhow. This simply builds muscle underneath at this point and you will get discouraged as the "tummy tire" will actually seem to be growing.

best post i have seen on mfp yet.. she is right.. fact of the matter is.. abs are made in the kitchen not the gym.. you calories are low but what are they.. cardio and great diet result in nice stomachs

If you are limiting yourself on calories to 1200 a day then you want to be sure you are not limiting your carbs too much as this is where you are going to get most of your sustaining energy. Eat good fats such as nuts and avocados. Nuts and avocados are high in calories and fat but they are just the right kind of fat. By eating these your body will let the other fat go as it does not feel the need to hold onto it.
Drink tons of water. The more the better. Take your weight and divide it by two, this number is the minimum of ounces of water you should be drinking a day.

I really do believe that you first need to address your caloric consumption - as in, you need to ensure that your caloric intake is adequate for how much you weigh and your current lean body mass (i.e. how much of you is not body fat). 1200-1300 calories is far too low in my opinion (for reference, my wife is also trying to lose weight and is 5'2" and her daily consumption is in this range). And don't necessarily trust those who say that you need to reduce your caloric consumption by 500 kCal daily to see results. The exact deficit will be dependent on what your total daily energy expenditure (TDEE) is currently. After you've calculated that, your percent caloric deficit should be no more than 20% of your TDEE.

And as another poster said, please, please, please, ensure that you're consuming foods from each of the three macronutrient groups in adequate amounts. You don't have to be a bodybuilder to be worried about how many grams of protein, carbohydrates and fats you're consuming. A good starting place is 40% carbohydrates, 20% fat, 20% protein, but there are calculations that can be done to ensure that you're consuming an adequate amount amount of protein for your lean body mass, enough fat to sustain healthy hormone production, and carbohydrates to keep you sane and keep your brain (which uses them primarily as fuel) properly working. Please send me a message on here and I can work with you to determine exactly what your daily caloric intake should be and how much of each macronutrient you should be getting. I've had a lot of experience with this myself and am happy to help.

Keep in mind that if your caloric deficit is too big, your body can start to go into starvation mode. It begins to match its daily expenditure to the limited amount of calories it's receiving on a daily basis. What's more, it actually begins to hold onto what fat you have as this represents the single most dense reserve of energy in your body.

As others have said, site-specific (i.e. lower abs, inner thighs, lower back) reduction of bodyfat is not possible. You need to eat at the proper caloric value first. Then we can talk more about what types of cardio (and in what amounts) do the best job at helping you lose weight.

Please message me when you get a chance.