For archival or educational offline use, here is a general guide on how to locate and install such a version.
Even in the "stable" 2021 release, users faced issues. Here are the fixes: Cs 1.6 Infinity Gigabyte Download -2021-
If you want a legal experience, buy the "Half-Life Platinum Pack" on Steam. Then install the mod over the legit files – though Infinity Giga typically requires a cracked steam_api.dll. For archival or educational offline use, here is