Short answers, pulled from the story.
Mamoru Shigemitsu and Yoshijirō Umezu accepted the Emperor's personal appeal to serve as the two signatories for Japan. Shigemitsu signed first at 9:04 a.m. representing the Emperor and Government, while Umezu signed at 9:06 a.m. representing the Imperial General Headquarters.
The eleven delegates left Tokyo by car early on the 2nd of September 1945 and boarded the USS Missouri at Yokohama. The ceremony lasted exactly 23 minutes starting at 9:04 a.m. when the first signature was placed.
The Japanese copy resides at the Diplomatic Archives of the Ministry of Foreign Affairs of Japan in Tokyo. It was last publicly displayed in 2015 as part of an exhibition marking the 70th anniversary of the signing.
Colonel Lawrence Moore Cosgrave signed below his line instead of above it due to being blind in one eye from a World War I injury. General Richard K. Sutherland crossed out the pre-printed name titles and rewrote them by hand to correct the relative positions for all subsequent signers.
One special flag flown from Commodore Matthew Perry's flagship in 1853 was displayed backward with stars visible in the upper right corner. This 31-star flag was so fragile that conservators sewed a protective backing on it to preserve its integrity before the event.