I am doing very light workout, e.g. 10 push-ups a day. I want to know that if I keep my diet to cereals with full-cream milk, will it have any effect on my belly fat?
Reiterating: Your body alone determines where fat is taken from or added. You cannot "target" an area for fat loss or gain. In 10 days, 10 push-ups a day will gain you 100 push-ups worth of tricep and pectoral strength, but will have no bearing on where your body decides to take fat from.
I've seen extremely obese people lose weight only on one leg for a month before starting to even out and lose in other parts of the body. It's rare, but it happens.
Eating cereals and milk only will not give your body all the nutrients you need, and you'll likely encounter health problems. Eating more calories than you burn will cause you to gain weight. Likewise, eating less calories than you burn is the only (healthy) way to lose weight.