Where are the 4 death mask in the Mystery Legends Phantom of the Opera?

In "Mystery Legends: Phantom of the Opera," the four death masks are located in distinct areas: one is found in the Opera house's attic, another is hidden in the catacombs, the third is located in Christine's dressing room, and the last is in the Phantom's lair. Players must solve various puzzles and navigate through the opera house to collect all four masks to progress in the game.