Which version of Visual Studio C++ to download for :
1 - Learn the syntax of C++ and try to use my new knowledge in MetaEditor.
2 - Maybe develop C++ code in Visual Studio and then use it in MetaTrader 4.
I think you need to be already experienced developer to use C++ code with MetaTrader 4 (via DLL?), as MQL4 is like C++ visually but its not the same.
If you are learning for now Id stick to one language and learn that depending on your goals. From posting history it looks like you just need to learn to code MQL4,
and gradually learn OOP principles as you go ?