The rules when put into effect after 9-11 said in order to get through security you must have a same day ticket. Initially they accepted just a confirmation but that was changed
requiring a boarding pass. I am not sure how far the TSA rules detals in order to get through security you must have a boarding pass for a flight in the secured area you are trying to access. I was turned away at EWR and MIA wanting club access but you can get usually get a pass from the airline.
Every airport is somewhat different regarding layout. I was in ATL over the weekend, a huge airport, when you clear security you have access to just about the entire airport
via the underground train. At ATL generally every terminal has different types of restaurants. I want to to McDonalds located in terminal E, i was flying Continental in Terminal D. No problem. It is not so easy at other airports. Many airports used to have alot of concessions pre-secuirty, but most new facilities being built most of the concessions are post security.