Short answers, pulled from the story.
The Indian Ocean raid, also called Operation C, was a sortie by the Imperial Japanese Navy from the 31st of March to the 10th of April 1942. Five Japanese aircraft carriers under Admiral Chuichi Nagumo struck Allied shipping, naval bases, and airfields around British Ceylon, sinking the aircraft carrier Hermes, two cruisers, and numerous merchant ships.
The British were forewarned by intelligence and sailed the Eastern Fleet before the Japanese arrived. Admiral Somerville refuelled at Port T rather than Ceylon on the 2nd of April, keeping his ships away from the Japanese approach. Japanese aerial reconnaissance failed to locate the bulk of the fleet, and Nagumo made no serious effort to search beyond the immediate raids on Colombo and Trincomalee.
Squadron Leader Leonard Birchall of 413 Squadron, Royal Canadian Air Force, flying a PBY Catalina designated AJ155/QL-A, spotted the Japanese Southern Force 360 miles south-east of Ceylon at about 16:00 on the 4th of April 1942. His aircraft transmitted the sighting before being shot down by Japanese fighters.
Hermes was attacked off Batticaloa on the 9th of April 1942 by eighty Aichi D3A Val dive-bombers held in reserve on Japanese carriers. She was hit by over forty 500-pound bombs and sank with the loss of 307 men. British Fulmars from Trincomalee arrived too late to intervene.
Malay Force, under Vice Admiral Jisaburo Ozawa, raided the northern Bay of Bengal concurrently with the main Ceylon attacks. Departing Mergui on the 1st of April 1942, the force sank 20 merchant ships and damaged three more in three days. Its aircraft also bombed the Indian coastal towns of Cocanada and Vizagapatam.
The Imperial Japanese Army refused to allocate troops for an invasion of Ceylon, so the operation was limited to a naval raid. After the raid, the Japanese carriers required maintenance and replenishment after months of continuous operations. By May and June 1942 those carriers were committed to the Battle of the Coral Sea and the Battle of Midway, ending any prospect of major Japanese operations in the Indian Ocean.