Tomb doors puzzle
Near the end of the game, you are in a tomb with infinite doors. You have to find the correct series of doors to progress. Go to the landscape view. Always start at the door with the face above it and go clockwise.
Hangman in A Prisoner Seeking An Escape level
When you reach the bottom of the chamber in the A Prisoner Seeking An Escape level, kill all the sand creatures and then enter the cell to the left when looking at the save point. In the left corner of the cell is a little joke on the wall. Take a closer look in first person view at the drawings you find there. Obviously the prisoners where playing hangman here.