You can do anything, but still within the limits of your authority.
You said that you had a copy constructor, even though it can't be compiled.
Well, if you don't align it, then you've already broken the rules.
On the dot.
There is no direct query. You'll have to infer it.
Just making things bigger?
Writing it down for posterity.
If there is a reference implementation, then use it as a check.
C++ language backward compatibility makes legal what you had hoped wasn't.
HBITMAP?
You can copy the bits into a DIB section.