What is the way for monsters to become immortals in Journey to the West?

As for the Monkey King, the Monkey King came to the Dragon Palace to make trouble in the underworld and was called the Demon Monkey. Later, he was named an official (even finished), that is, he was included in the immortal book and became a fairy. He thinks the official is small and opposes the lower bound. There are some demon monkeys, whose official name is the Monkey King, also known as fairies. In fact, in The Journey to the West, the biggest difference between a fairy and a demon is whether there is a seal, just like the Water Margin has no seal.

Monsters eat the meat of Tang monks just to live forever. The Journey to the West mentioned that monsters will be robbed every 500 years, but they will disappear (immortals can eat flat peaches every 500 years). Therefore, eating Tang Priest can make you live forever. Just snap up all the monsters who believe in it, just to live forever, nothing else.