Huh?
They made the originals.
Then the Final Mixes of the first two games a year later, but those were only ever released in Japan.
Then 1.5 Remix (an HD update of the Final Mix versions of the original game that was available worldwide, plus the GBA sequel Chain of Memories, plus the cutscenes from the DS game 358/2 days).
Then 2.5 Remix, HD update of KH2 Final Mix, plus Re: Coded (the phone game), plus Birth By Sleep (the PSP game)
Now 2.8 is Dream Drop Distance (the 3DS game...note we're up to 5 different consoles now), and a pair of short films filling in some extra backstory stuff.
It's all different games, in other words, not special editions of a single existing one, unless you count 1 and 2 getting their special edition counterparts instead of the originals. They were made so everyone could play every game on a single console before KH3 comes out.