Press Home. Press Contacts. Go to that contact. No app needed.
--- i got that part. I meant when a contact is calling me, and the screen pops up with their name and a pic or blank person. An app that that will allow more info about that contact when they are calling you or you are calling them
If you mean wifi from the phone to a laptop or other device, using your phone's data connection, it depends on your carrier. For instance, with Verizon the only way to do it is to pay for a tethering plan. They'll block a tethered connection if you don't. Otherwise, there are many apps that will do it, no ROM or root needed.