By Chuck Mikolajczak NEW YORK (Reuters) -The Nasdaq scored its first gain of at least 1% in 2024 on Monday, as a fall in Treasury yields helped lift megacap stocks, while a sharp drop in Boeing shares kept gains on the Dow Industrials in check. Megacaps advanced, lifting stocks such as Amazon.com which closed up 2.66% and Alphabet, which rose 2.29%, as Treasury yields fell ahead of readings on inflation and a new supply of government debt this week, with the benchmark 10-year U.S. Treasury yield hitting a low of 3.966% on the session. In addition, Apple climbed 2.42% after the iPhone maker sai…