Will swimming freestyle for an hour everyday make my shoulder broader? Also, What type of diet should I eat in order to reduce the belly fat? Does swimming alone help me reduce all the belly fat?

I have no idea if swimming makes your shoulders broad. If you work out, your muscles will tone and grow. If you have wide shoulders, they might seem broad with the muscle mass but then again they might not.

Your body has a certain fat distribution and it grows and shrink with your body fat percentage. For example, if you have a chubby belly, thighs, and arms. If you work out just your legs, IE, cycling, you're body will mobilize the fat from ALL places and not just your legs. It honestly doesn't matter where or how your do your work outs, your body will mobilize your fat equally. So if you think that just doing crunches, situps, and ab workouts will get rid of your belly fat, you're going to be disappointed. You'll still have great abs, washboard like and chissled, but they'll be unseen because they'll still be under a layer of chub.

Swimming is a great way to burn calories. It is low impact on your joints and tones your body beautifully. If you combine that with a proper diet then you're on the right track to lose weight. I will give you the secret to losing weight and it is a simple one. You have to run a caloric deficit while getting all the energy, nutrients, and vitamins that your body needs. That is all there is.

A healthy diet is different dependent on who you talk to. A vegan will have a MUCH different idea compared to a carnivore or an average joe. Some basic principles are:
1). Shop the U. The fresh foods, meat, produce, dairy, and grain, are all around the outside of the store. Shop there and prepare your own meals. You know what is going in and you don't need to worry about hidden sugar. For example take a tomato based sauce. There is a bunch of salt added to enhance the flavour as well as a bunch of sugar to mask the brine of the salt. You get a balanced flavour but with a butt-load of salt and sugar. Prepare it yourself and you'll have a tasty sauce but with out those and other additives.
2). Balance the amount of grains, meat, and veggies you consume. Going all protein and eating a cow a week will sustain you but it won't be healthy. The same if you're consumed by veggies. You need a balance of all them, so you get all your nutrients and vitamins and calories and don't have to take supplements.
3). Avoid processed sugar and processed foods. A lot of these foods get their energy mobilized quickly. When your body has an over abundance of energy it starts to pack it away as fat. You can be at your caloric level but since you're getting them quick spurts, you will have them packed on you. A lot of natural foods mobilize their energy slower and sustain your energy levels better. This also gives your body a good signal of constant and reliable food availability. This will get it away and keep it away from starvation mode. It will be more likely to burn and dispose of excess energy and fat. Giving you a better weight lost potential.
4). Figure out how much energy you need for a day that includes exercise and run about 2-300 calories below that level. I am not sure how many you should be running low but you need to. This will send to your body the message that while you're consuming enough, you need more energy so burn a little of that fat. This is the key to weight lose. If nothing else this is what you need to pat attention to.

Good luck.

Thank you so much for your advices @cravenmorhead. :) I will start a healthy diet from today.

I think any type of swimming will help with that actually. Not necessarily freestyle.

I agree with peachey on this. Any time of swimming that concentrates on the muscles in the upper arm, will make the shoulders 'appear' broader. In particular, the deltoids.