If I'm not mistaken, Visual Studio only refers to the IDE used to write and compile with.
Having different .NET versions should not affect programs that don't need them.
In SDR# folder there is a file called "crash.txt" this points to problem. Not that it will help to much as we can't do much about it with out the source code (which was available at one stage.)
The 1666 SDR# I used was a new install just to test this issue with.
My 'SDRSharp.exe.Config' and 'Plugins.xml' are default with the exception of this added line in plugins.xml:
<add key="CTCSSDecoder" value="SDRSharp.CTCSSDecoder.CTCSSDecoderPlugin,SDRSharp.CTCSSDecoder" />
I don't think order matters except for positioning in sidebar of SDR#. In any case I placed it before "Signal Diagnostics"
Not sure about DSP plug-in, If I get a second I'll have a look.
My CTCSS setup detected tone on this setup.
Yes, the bright spark who created these files (.dll,.txt, .zip) have made a conscious decision to make all these files the same date/time with only visible difference been the size. (or MD5 hash)