> images for different platforms (Mac, Linux, Windows)
yes
It is the responsibility of the VM to contain the differences. Note that there's some "platform-specific" code, but the image contains the code for all platforms at once.
Generally speaking you can code on one platform, copy the image files to another and continue your work (although doing this can cause trouble, as e.g. some file paths may now point to non-existing locations).
> VMs (32bit, 64bit)
yes?
the files are different, but I don't know if there's code difference, or if the images are just built with different memory layouts
Peter