The program is designed to instantly close any versions of GTA. The program must be placed in the same folder as your .exe...
By default there are 3 settings:
gta_sa.exe
gta-vc.exe
gta3.exe
If you put in the first field 0, then you can install your .exe. This function is in case your .exe is different from the usual ones or it is not SA, VC, III, but another version of the game...
To close GTA, press F4
How to close the program itself is shown in the fourth screenshot.