And about CD reprints - the child album must have the same tracks as parent album. So if it has even one less or one more track, it's not a child album.
CD child album must have different looking printed material - different front cover or different back cover and such, anything like that really. Even a different catalog number is enough I think.
Or even track names in another language, like:
http://vgmdb.net/album/33334 (child)
http://vgmdb.net/album/29678 (parent)