What things can you do in a iPhone 4?

I might get one for my bday

You can do an experiment that involves emerging the phone in acid. That's pretty much it.

NO! Do not get that. If you want an iPhone, get the 5. I myself would not recommend getting any iphone though because they are horrible. You should look into getting a galaxy S3 or a different android smartphone.

Everything a $200 android phone can do but for x2 the price

You can do many things with it, I'm gonna give you a brief list of what you can do with an iPhone 4:
Watch TV (Justin.tv)
Translator (Google translate app)
Browse on the Internet (there are many web browsers for iPhone)
Make free calls and free messages (Viber)
Messenger app
View, edit and save Microsoft office documents (DocsToGo)
Use it as a GPS device
Make video calls (Qik Video, Tango, Facetime)
Control your computer using your iPhone (Teamviewer)
Edit your pictures (CamStar, Instagram)
Radio (iheartRadio, Pandora)
Share photos with another iPhone (Bump)
Play HD games
and much more…

Hope this helps you buddy