Stage 6

Level 6-1
Level 6-1 is a hidden level after 5-10. It is unplayable under normal means and can only be accessed via hacking. Steps will be included below on how to unlock Level 6-1

Cheat Engine Required
You need Cheat Engine to access this level, if you do not have Cheat Engine, simply go and download it at the Cheat Engine website.

Now that you have everything, the first thing you want to do is open Cheat Engine and click the blinking computer icon. Go to the buttons below and click "Open File". Then locate your userdata file, then open it with Cheat Engine. After opening your userdata file in Cheat Engine, click "Add Address Manually" and type 4 into the address box. Now change the address's value to 51. If Adventure mode does not say "Level 6-1", simply go to another user or create a new one and alternate until the user file you modified says "Level 6-1". If your game crashes upon changing the address value, simply re-open your game.

Trivia

 * It takes place in the front yard. One would assume stage 6 to take place on the roof at night.
 * It has the same zombies as Level 5-9.
 * It is apparent that this level was not intended to be in the game.