how do you get out the the thing when you stab ms lemons with a knife

You need to buy the skeleton head first, try to stab him then.

I don't work at Oxtord Games but I'll try and help you, based on what I understood you want to reset the game, if so, follow these simple steps:

1- Press Windows + R keys on your keyboard.

2- Type in the app that has opened (called "Run"), "%appdata%".

3-From there, a folder will open, find and open "MMFApplications". 

In there you will find (probably other games too) OuroboroS, MsLemonS, MrTomatosV2 and Resolution v1, you can reset everything (Resolution v1 isn't a game btw), if you want to save your progress copy the file and put it somewhere else, to reset everything, instead, delete the file (or drag it somewhere else). If you need more help add me on discord Lino#5541.