Short answers, pulled from the story.
Sushi originated in the Mekong River basin of Southeast Asia where fishermen preserved freshwater fish by packing it into fermented rice for months at a time. This ancient technique known as narezushi relied on lactic acid to prevent spoilage during the rainy season when fish flooded rice paddy fields.
Around 1824 chef Hanaya Yohei opened a shop in Ryōgoku Edo and introduced nigiri-zushi to the chōnin merchant class. The original nigirizushi was about three times larger than modern versions and used half the vinegar developed by Nakano Matazaemon founder of the company Mizkan.
The California roll emerged in Los Angeles and Vancouver during the late 1970s with credits given to chefs like Ken Seusa Ichiro Mashita and Hidekazu Tojo. Tojo claimed he created the inside-out roll at his Vancouver restaurant naming it after the state abbreviation C.A. for crab and avocado.
Large marine apex predators like bluefin tuna can harbor high levels of methylmercury posing developmental risks to pregnant women and young children. EU regulations now require raw fish for sushi to be frozen below -20 °C for at least 24 hours to destroy parasites.
In 1958 Yoshiaki Shiraishi opened Genroku Zushi in Higashi-Osaka introducing conveyor belt sushi to casual diners. Plates of sushi travel along belts past tables with bills calculated by counting colored plates or using barcodes and RFID tags embedded in dishes.