I m 15, will loose skin around my breasts snap back after weight loss?

We can't know. If we said it wouldn't snap back, would you just not lose the 30 lbs? Ultimately, it doesn't matter because it's better for you to be at a healthy weight and have saggy breasts (that's what bras are for) than to be overweight.

At your age, chances are you won't have much of a problem with loose skin unless you lose the weight too fast (in an unhealthy manner). If you lose it gradually, your body will have time to adjust and that will increase your odds of not having flab when you reach your goal.

Some women don't lose breast size when they lose weight over the rest of their body. Some do. Your breasts may not decrease in size, or at least not much. Depends on your body. Mine do get smaller when I lose weight. My mother's don't (but hers stay small all the time, even when she's very heavy)

I had the same problem when I lost 10kg but now im doing push-ups and exercises for chest and my babies Look better