This sixth iteration of the C# language is provided by the Roslyn compiler. This compiler came out with version 4.6 of the .NET Framework, however it can generate code in a backward compatible manner to allow targeting earlier framework versions. C# version 6 code can be compiled in a fully backwards compatible manner to .NET 4.0. It can also be used for earlier frameworks, however some features that require additional framework support may not function correctly.
Visual Basic 14 is the version of Visual Basic that was shipped as part of Visual Studio 2015.
This version was rewritten from scratch in about 1.3 million lines of VB. Many features were added to remove common irritations and to make common coding patterns cleaner.
The version number of Visual Basic went straight from 12 to 14, skipping 13. This was done to keep VB in line with the version numbering of Visual Studio itself.
C# 7.0 is the seventh version of C#. This version contains some new features: language support for Tuples, local functions,
out var declarations, digit separators, binary literals, pattern matching, throw expressions,
ref return and
ref local and extended expression bodied members list.
Official reference: What's new in C# 7