OK, so the original game was made with rpgmaker vxace (I think, not positive), and had stability issues with some of the plugins in addition to many bugs. The art was improving over time in the original version, with some honestly very bad pieces and a lot much better. It was never finished, since the developer switched to RPGMaker MV.
The developer is chinese, but there's basically no story at all in the original or remake version. What is there has been translated as development went on, but again there's not much there.
The remake is basically the same game with far better game balance, better art, and more content. I don't think it's considered a fully complete game yet, but it may just be at the point of bugfixes, I don't know.
There's also the advance version, which is a mod of the original version (made with permission, since that's been a topic of issue with one person recently). It has more story and has far better game balance than the original and has both added story content and uses art from the remake version in addition to the original version.