There are 2 ways of determining the software version of a smartwatch:
1. One can determine the smartwatch version based on the watch model. On your watch, swipe up on the home screen and select the Settings icon. In settings scroll down to the About watch option, where you can find the exact model number of your device as well as Software information.
Pixel, Galaxy Watch 4, Watch 4 Classic, Watch 5 and Watch 5 Pro and future models are running on Wear OS 3.
Mobvoi Ticwatch, Fossil, Suunto are running on Wear OS 2.
Gear, Galaxy Watch 3 and earlier, Watch Active are running on Samsung Tizen.
In order to determine Tizen version open settings menu, choose About watch tab, Software and check Tizen version.
2. You can view Watch settings on your mobile device as well. Open Galaxy Wearable application on your mobile device, choose Watch settings option, open About watch tab, where you can find Software information (Wear OS version).