Acronym Soup: RHIP?

Questions

Poet Robert Frost & the white mountains, both call this state home?

Process of heat treatment by what glass & certain metals & alloys are rendered less brittle & more resistant to fracture?

Few people know how to be old Who by?

Republic in southern central America, bounded on the north by Nicaragua, on the east by the Caribbean Sea, on the southeast by Panama, & on the southwest & west by the Pacific Ocean?

Several different ways in what printing may be accomplished, such as lithography, letterpress, flexography, gravure, & screen printing?