Yup. They also were not developed by the same company. 3.5 and 3.9 were developed by Haage & Partner, 3.1.4 and 3.2 were developed by Hyperion Entertainment.

Yup. They also were not developed by the same company. 3.5 and 3.9 were developed by Haage & Partner, 3.1.4 and 3.2 were developed by Hyperion Entertainment. There's even an AmigaOS 4.0 from Hyperion which is PowerPC only. For extra bonus points, there's MorphOS which is a heavily AmigaOS influenced OS. PowerPC only, runs on some of the older PPC Macs. And there's also the open source AROS reimplementation of AmigaOS 3.1 (with a lot of extras). (I'm sure I got a lot of details wrong, been years since I last did Amiga stuff.)