This achievement is only achievable by changing the save file data. So you are not able to get this one by playing the game. We need to make our own... yeah, kind of Test Level Loader (like the option to load test levels of games via dolphin emulator for example).
But we need to corrupt our files, so yeah, you need:

• The game itself obviously
  
• A program to edit .json files, I like to use the free software Notepad++
  
• some knowledge of computers haha

Let's get this bread!

Okay, so to understand what is going on, you need to know that every level or stage got its own data file. To find these, you need to go into the "local data" of this game.

In your game library, right click the game and go to properties -> local data -> search through local data . You now get access to the game files. Now you can go to the folder Vectronom_Data -> StreamingAssets -> Data -> LevelData.
Now you can see every level.

Now type %appdata% in your search bar on Windows 10 and hit Enter. Go back one folder and click on the folder LocalLow. Now follow this order: Click through the folders Ludopium -> Vectronom -> savedata.

Next up you need to backup your data.json. Please copy and rename it so you can change it back later, because we're going to change the file now.
You're ready to open the data.json file with a program like Notepad++.

Hooray! We're prepared now. You could close this guide now if you want to find out everything on your own. At the end of this guide I will feature some cool extra stuff, so you might come back later on. ;-)

Now you need to understand the level data files. There is a file for every level like "Sidestep", "Witchcraft" and so on, plus, there are some data files for the HUB world and the Result Screen, which is also a stage. These ones are called "GOLD HUB" and "PRIME T ZONE". By opening all of these files, you can see the name of each level right at the beginning of the code. If you look at the data.json file with a json formatter (you can search for it online), there are 2 levels mentioned, which aren't completed (if you already cleared every level ingame). These are the HUB and the Result Screen. So don't worry about that.

But there is also one other file by utzstauder which is named "TestLevel2000" inside the code.
This one is the hidden debug level! Congrats, you found it, but to get the achievement, we need to play this level, too. :-(

To do so, you need to do the following steps:

• Copy the name of the level data ID, that would be: 2018-08-17-00-03-41-936-Gyrgy (UPDATE)
  
• In the data.json file at the beginning, search for lastLevelVisitedId and replace the following level ID with the one you just copied.
  
• If you completed the game, you need to search for the following "flag": finnish_last_level. You can do so by pressing CTRL+F to find it. The value is set to true and you need to set it to false.
  
• Save the data.json file and close it.
  
• Now open Vectronom and press Continue (The button that normally sends you to the HUB)

Congrats! You now entered the HIDDEN DEBUG LEVEL "TESTLEVEL2000" and
earned the achievement "JASON" !!

DON'T FORGET TO REPLACE YOUR SAVE FILE AGAIN!

It should look like this:

So you might ask what else can be found in the data. If you replace the ID with the T ZONE PRIME you end up at the result screen with literally no content at all. The ID is called: 2018-08-17-00-03-41-936-Gyrgy (OUTDATED?)

It looks like this:



If you enter the ID of the GOLD CREDITS, you end up in the menu with the credits playing on the small screen. The only way to close the game is by doing it outside of the game, because the menu is corrupted afterwards. ID: 2019-04-22-18-22-11-893-drost

It looks like this:



If you want to look through all the assets of the game, you need to download the Unity Assets Bundle Extractor[7daystodie.com]

With this program you are able to access 4 .assets data files in the Vectronom loca datas. In there, you can find thousands of textures, objects, ..... and even some upcoming content, hopefully... :-)

Thank you for following my first guide :-)
I hope I was able to help you. Please leave some feedback in the comments. Do you have any questions? Write them in the comment section, too!

Greetings from Germany, Pascal.