[Prophet in the wilderness]

Well, the first prototype of the 747 was only used for static tests, and the 3 rd 747 was literally broken into pieces while they tested it for it's engineering limits and fatigue tests.
The first 747 was also used in other tests, as in the flying testbed platform for testing the first engine for the 777.
The first 747 prototype is loaned out to a museum now ( I wished the Smithsonian - Air&Space Museum would have gotten it).

[Paleo Conservative]

The first 747 prototype is loaned out to a museum now ( I wished the Smithsonian - Air&Space Museum would have gotten it).

It was used to flight test the PW and RR engines for the 777, and it has been used by Boeing for flight testing various other equipemnt.