the latest released and nop the floor remain the same like there is no lich when i get inside again
I'm having this same problem actually on version 5.1. When you enter the Lich cave, it automatically starts you on the highest floor you last visited instead of Floor I, so I can't go back to try the Lich Pool event.
EDIT: You can reset the dungeon with one of the ladder escape items you get from entering it, it will always reset at 1 so you don't have to redo anything to get the Lich event to work.