/std:only works for c++14 or c++latest (and c++17 in latest VS2017).
You don't have to do anything special to enable [C++11] features.
Marked as answer by Jane Wang - MSFTMicrosoft contingent staff
|To completely disable C++11 features in Visual Studio, you must compile with a toolset old enough that it does not have any C++11 features. The last version of Visual Studio to have no C++11 support was VS2008 (question about that here: Visual Studio 2008 with c++11).|
To use an older toolset, you must first install that version of Visual Studio, and then modify the "Configuration Properties->General->Platform Toolset" and set it to the appropriate Visual Studio version. When you compile with Visual Studio 2008 toolset, any C++11 usage will be errors.
|you'll need to find a compiler that doesn't support any C++14 features, good luck on this.|