Short answers, pulled from the story.
Apollo 16 was crewed by Commander John Young, Lunar Module Pilot Charles Duke, and Command Module Pilot Ken Mattingly. All three were announced as the prime crew on the 3rd of March, 1971. Young was 41 at the time of the mission, while Duke and Mattingly were each 36.
Apollo 16 landed in the Descartes Highlands, a region of the lunar highlands chosen because scientists believed it had been formed by volcanic activity. The specific landing site was between North Ray and South Ray craters, and the Lunar Module touched down on the 21st of April, 1972.
Big Muley is the largest rock collected during the Apollo missions, a breccia retrieved by Charles Duke from near Plum Crater during the first moonwalk of Apollo 16. It was nicknamed after mission geology principal investigator William R. Muehlberger. The rock was one of 95.8 kg of lunar samples returned by the mission.
Apollo 16 proved that the Descartes Highlands were not volcanic in origin, contradicting the leading pre-mission hypothesis. Analysis of samples confirmed the Cayley Formation was not volcanic, and geologists concluded there are few if any volcanic mountains on the Moon. The mission also detected two new auroral belts around Earth.
During pre-undocking checks, Ken Mattingly detected oscillations in the backup gimbal system of the command and service module's main engine. Mission rules required the lunar module to hold position while NASA managers considered aborting the landing. After several hours of analysis, controllers determined the problem could be worked around and authorized the descent.
Charles Duke was 36 years old when he walked on the Moon during Apollo 16 in April 1972, making him the youngest of the twelve astronauts who walked on the lunar surface during the Apollo program. No younger human had walked on the Moon as of the time of the mission.