Ah, welcome to the final boss. 99% of players couldn't make it alive without additional hints. A hint of "Look back to your journey" is already given. So what have you done in this game? You collected 7 items! "1 3 7 4 2 5 6" must mean your inventory and each of their position. So 1 is the key you found in locker room. Which picture represents the locker room and the item's position? Your turn.