But anyways from what I understand you need to know how to edit the "Simpsons.exe" file to do that. There's other things that are also inside that file such as the keyboard controls, cheats, and the needing-the-CD function; as opposed to external folders which have the sound files, artwork files, texture files, mission scripts, and purchasing vehicles/clothes scripts, etc.
Editing .exe files isn't nearly as easy as editing the external files for this game which are an English-language coding that you can simply edit in Notepad or whatever. You'd need to use a software such as x32dbg/x64dbg to edit the .exe file and change or remove the coding that makes it so the game can't have more than 7 levels. I know what those programs do but to actually use them fluently, hopefully one of the admins can do that.