Thanks for your detail, I should definitely do that.Yup, if screens.rpy doesnt exist within rpa, then the game shouldn't be able to run since screens.rpy contain the main menu script. However, if you see no screens.rpy after you extracted it, search for screens.rpyc.
Rpyc extension is ren'py rpy that has been encrypted. If that is the case, you might want to use .unrpyc. There should be an instruction at how to extract rpy from rpyc file in the website where you downloaded it.
After you got your rpy file, you can finally use my method.