The official Black Ops II Steam Store page provides the full game with guaranteed compatibility and support for modern Windows versions (Windows 10/11).
Intel Core 2 Duo E8200 2.66 GHz or AMD Phenom X3 8750 2.4 GHz. The official Black Ops II Steam Store page
For the most stable and secure version, it is recommended to use official platforms: The official Black Ops II Steam Store page