The ".part1.rar" file extension itself isn't problematic; it's a standard way to split large files. However, issues arise when this file or its associated archive is corrupted, incomplete, or improperly cracked. A corrupted "GTAIV4CE.1.1.3.0.part1.rar" can prevent users from successfully extracting the game files, leading to errors when attempting to play the game. These errors can range from simple extraction failures to critical game launch issues.
This update, released around late 2016 and updated in 2018, focused on modernizing the game's compatibility and fixing long-standing engine bugs: : Added checks for Windows 8, 8.1, and 10.
: Specifically addressed a bug in the final mission, "Out of Commission," which became impossible to complete when the frame rate exceeded 60fps.
Version 1.1.3.0 is a popular "middle ground" for modders who prefer the standalone EFLC over the newer Rockstar Games Launcher-integrated Complete Edition: