The answer would be false
It's better to target a specific fitness goals at a time and improve the areas that will be useful for you
Soccer athletes for example, will only train to achieve a specific fitness goals for their roles on the field, so does American football ( i.e : Overtraining in strength area will be useless for a receiver)
I do not think if you became a Pro-Screamo at your age you would strip your throat out
When it comes to Physical Fitness diet is very important. Imagine a person who eats only fast food but expects to be fit like an athlete. The truth is you can only do so much with exercise alone. The food a person eats is essentially the fuel for a person throughout the day to create energy and get nutrients. Think of a car that needs gasoline and oil. If you pick the wrong kind of oil it can have an affect on the lifespan of your car and without gas the car will not run.