I don't think you can mate a V4, 4.5, 5 (of course!), and 6 (of course!). If you mate them together, for example a V1 Tarakotchi mates a V2 Chohimetchi, Chohimetchi will appear as a Nazotchi on the V1 and Tarakotchi will appear on the V2 as Nazotchi as well. Hope I helped and yes they can mate!!!