What app can you use to make your pictures look all professional looking?

But I mean, just by using your iPhone 4. Is there any app for that? I don't like how in the regular camera the pictures look grainy. And there's this girl on Instagram who only uses her iPhone and her pictures are just perfect.

Now just how do you think photos looked "professional" 100 years BEFORE there was any such thing as an "app"?

Your question, and your convoluted mindset, is a shining example of what the lunacy of digital devices has done to dumb down what people THINK is photography. It is NOT a phone and apps. It is a person who is skilled in the use of the proper equipment.

Maybe your question is a joke. I sure hope so, … But it likely is not. Pathetic.

Professional-looking pictures are the result of professional-level skills; there's no app. IPhones can take excellent pictures, but under a much narrower range of conditions than a professional camera, so start by learning what the limitations of your phone's camera are. Among other things, make sure you have adequate light, avoid (or learn how to deal with) high-contrast lighting, and watch out for glare on the lens.

Apps are to photography what autotune is to popular music.

Apps are not the answer to all the world's problems!
Skill also plays a big part in getting things right.

Phones and phone apps are not used by professional photographers for taking and editing photographs.

APPly some time and effort to learning photography.

If you can master (or at least understand) the basics of lighting and composition then you don't need an app at all. Almost 80% -- even more -- of what makes a good photo great is simply the use of good lighting and composition techniques. Most special effects photography makes spectacular use of this simple fact.