Short answers, pulled from the story.
Operation Mo was a Japanese plan to seize Port Moresby in the Australian Territory of New Guinea, with the broader goal of isolating Australia and New Zealand from the Allied United States. The plan was developed by the Imperial Japanese Navy and backed by Admiral Isoroku Yamamoto. It was formally approved by Japan's Army and Navy General Staffs in April 1942.
The Japanese Navy General Staff had been considering Operation Mo since 1938. The directive was conceived that year with no specific date set for its execution, pending earlier Japanese successes during the first and second phases of the southern conquest. It was formally approved in April 1942.
Rudy Fabian was a United States Navy codebreaker working at the intelligence unit FRUMEL who decoded Japan's plans for Operation Mo before the invasion began. He briefed General MacArthur on the 9th of April 1942, showing him an intercepted message that identified the attack on Port Moresby as an invasion rather than an air raid. MacArthur was initially incredulous, having expected New Caledonia to be the target, but Fabian demonstrated the JN-25 code-breaking process and showed him the Japanese commander's intercepted message.
The Battle of the Coral Sea stopped Japan's seaborne invasion of Port Moresby. The light carrier Shōhō was sunk, the fleet carrier Shōkaku was damaged, and air groups from both fleet carriers suffered losses severe enough that they had to return to Japan to re-equip and retrain. Japan's Moresby invasion transports reversed course northward and the sea landing was abandoned.
Operation FS was a component of Operation Mo that called for Japanese assaults on New Caledonia, Fiji, and Samoa, intended to extend Japan's defensive perimeter deep into the Pacific. It was suspended on the 11th of July after Japan's remaining carrier strength was destroyed at the Battle of Midway. The suspension ended any prospect of the broader Pacific isolation campaign that Operation Mo had envisioned.
After abandoning the seaborne invasion, the Japanese Army attempted an overland assault on Port Moresby via the Kokoda Track across the Owen Stanley Range in New Guinea. That campaign also ended in Japanese withdrawal. Port Moresby was never taken by Japan.