S.W.A.N.: Chernobyl Unexplored

Near the end of game when you are in floating bedroom it will have 2 doors, 1 in the middle and 1 on the side, there will also be 2 pools of blood on the floor (Grey and Red). Above the door on side there will be a code 1986 colored in Grey Red Grey Red digits, after passing through the door there will be 9 doors on your left. The closest one to you is 1 and farthest away is 9.

First you'll want to step in grey pool to change the colour of doors to greyish and open the door 1 to move the number 1 from side door to the door in the middle of the room, repeat the same process for remaining 3 digits, stepping in red pool of blood for door number 9, then grey pool and for door number 8 and finally red pool again for door number 6.

Once 1986 is above the door in the middle of the room, open it and achievement will pop