I have some questions about using Microsoft::VisualStudio::CppUnitTestFramework and Test Explorer for native C++ projects in Visual Studio 2012.
For more information, see Organizing C++ Tests.
For the first question: You can't. You should write your unit tests in a way, that they do not interfere with each others results.
Second: The only way to do that is with reflections. Again I do not recommed it. If you feel, that there are private method that should be tested, that is almost always the sign of that you should divide your class into smaller classes.
Third: The Visual Studio test framework is fine, if you do not have any specific need to look for others, then just stuck with it.
And good luck with unit testing :) If you feel a little lost, let me recommend you this book:
It explains everything you need.