Windows 3.1x

Windows 3.1 (codenamed Janus) is a series of 16-bit operating environments produced by Microsoft for use on personal computers. The series began with Windows 3.1, which was first sold during April 1992 as a successor to Windows 3.0. Subsequent versions were released between 1992 and 1994 until the series was superseded by Windows 95. During its lifespan, Windows 3.1 introduced several enhancements to the still MS-DOS-based platform, including improved system stability, expanded support for multimedia, TrueType fonts, and workgroup networking.
Windows 3.1 was originally released on April 6, 1992; official support for Windows 3.1 ended on December 31, 2001, and OEM licensing for Windows for Workgroups 3.11 on embedded systems continued to be available until November 1, 2008.
Updates.
Windows for Workgroups.
In November 1992, Microsoft released two versions of Windows for Workgroups: 3.1 and 3.11. 
Windows 3.2.
In 1993, Microsoft released Windows 3.2, although only released in China.
Windows NT.
On September 27, 1993, Microsoft released Windows NT 3.1. It was the first Windows NT version. It has better programming and more features. Windows NT is not a true update to Windows 3.1 as it does not share any kernel code with Windows 3.1. Instead it is based on the new 32-bit Windows NT kernel.
References.