Roslyn and .NET Runtime version [duplicate]

Answer 1

As of now Roslyn C# compiler and tooling cannot run on .NET 4.0

You can certainly cross-compile for .NET 4.0, but to run the compiler itself you need at least .NET 4.5

Answer 2

The new C# 6.0 features don't depend upon framework support so yes, you an app compiled with the C# 6.0 compiler will run on .NET 4.0, assuming of course you specify you are targeting .NET 4.0 in your project file in the first place.