In order to make sure your account does not get suspended or banned, you will need to switch into guest mode.

To do this, simply log out of your Infinitode account in the top left corner of the game window

The secret level we will load is 'sandbox.json'
To access the 'sandbox.json' level, go to infinitode 2 in your steam library, click the gear icon then go to properties> browse local files. From there you will see the games files (obviously). You will also see the levels folder, inside of there you will need to find 'sandbox.json' and open it with a text editor.
Inside of that you will see 5 data values.
name = The name of the level (Duh)
stage = What stage the level is located in
stagePosition = What space the level goes in the assigned stage
hasLeaderboards = does the level have leaderboards?
difficultyMilestones = What milestones do the player need to achieve to win that level?

The 3 that we are interested in are the stage and stage position values (We also might want to disable leaderboards just incase)

I changed the stage value to 0 and the stagePosition value to 1.
I also changed hasLeaderboards from true to false

If you have the game running, close it.
Start the game and go to the story mode, then load the 'sandbox' level and turn on auto mode.
The level is actually hard to lose so just keep the game running.