and look for "Microsoft .NET Framework 4.0". You can also verify via the Registry Editor

Essential for specific tools and games that target the 4.0 version specifically.

The 4.0 release introduced several breakthrough features that changed how Windows applications functioned:

Though Microsoft has since released .NET Framework 4.5, 4.6, 4.7, and 4.8, the original 4.0 version holds a unique place. It introduced core technologies like the Task Parallel Library (TPL) and Managed Extensibility Framework (MEF). Many custom line-of-business (LOB) applications built between 2010 and 2015 were compiled specifically against version 4.0. Simply installing a newer version does not always guarantee backward compatibility for these legacy apps.

The .NET Framework 4.0 Redistributable 64-bit is important for several reasons:

Microsoft .NET Framework 4 (автономный установщик)