Is it possible to get the address of the stack in C++?
Yes, but not through any published API if I recall (I may be wrong on that).
I recall seeing several private functions in private libraries that can be called, if you know the correct function signature and the calling nature of the function (stack based or register based).
It's possible to store assembler instructions as numbers in a C++ array.
Yeah it's pretty cool too. It's also possible to just shove that list into some arbitrary location (I.E. outside of any process in mapped memory) and then jump to it. I did do that exact thing to call kernel functions that have no API what so ever.
If you need to return from the code you need to manually manipulate the registers so that you don't crash the system (done that one before too).
Fun stuff that is.