1) Why did he remember the time of his early childhood? (reading for the main idea)

Roald Dahl remembered this time because of a memorable conversation he had with his father about liquorice bootlaces. His father warned him not to eat them, explaining that they were made from rats' blood and that ratcatchers could become millionaires by selling rats to the factory. He also mentioned a fictional illness called "ratitis" that could be caused by eating them.