My post is not "how to", there are no steps, only answers on your questions.
Here again - answers on your questions:
You asked about MapSource versions and that was answer - some MapSource versions posted on forum are made this way - converting IMG files to MapSource version.
Yes, just copy gmapsupp.img to map folder, this folder should already exist on your device (this one is not hidden as system folder)
It should be in root of device, or root of SD card, if it's not there crate it, yes device will recognize gmapsup2.img.
No new JCV folder needed, just put new *.JCV file in same folder (no renaming needed as they already have different names).
New (second) gmap3d.img rename to gmap3d1.img and put in same folder where firs one is (maximum 2 files) - as explained by tom1807 in post #2 of this thread.