The PSP releases are a port of the original Japanese PC game with the rhythm bar removed. The 2015 release is a remasted version of the original PC game. The game had to be remade for the 3DS, 'Gurumin 3D: A Monstrous Adventure'. It is a port of the remastered version that has been changed to better fit the systems controls and use the 3D feature.
"Gurumin: A Monstrous Adventure is a fantastic Action-RPG from leading Japanese developer Falcom (Developers of “Ys” and “Zwei” among other classics) featuring real-time combat, stunning 3D graphics, tons of fully voiced characters and mini-games , 90+ items, multiple endings, a rocking soundtrack, 35+ hours of playtime, and more.
Originally released outside Japan on Sony’s PSP, Mastiff is proud to bring a fully localized and updated version of Gurumin: A Monstrous Adventure to Windows and to offer it through Steam with a full set of Steam specific features including Achievements, Trading Cards, Big Picture and Cloud Save."