Once Abhimanyu Mishra and his father bought one-way tickets to get them from Englishtown, N.J. to Budapest, there was no turning back. The pandemic was still raging, but that tiny pathogen didn’t stop the countdown clock separating a 12-year-old boy known as Abhi from history. Mishra was on a mission to become the youngest ever chess grandmaster. “It was very scary and we knew it was a big risk,” Abhi said. “But we needed more tournaments. We had to try it.” For 77 days over the summer, Abhi and his father Hemant lived out of a Hungarian hotel room that...