Does that mean if I choose 4.0 then the Apps would be launched ONLY on the 4.0 wearable device?

But the latest version of my Gear Sport is v3.0. And I tried run the v4.0 project on the v3.0 device, it is also runnable.

So if I want create a application for my v3.0 Gear Sport, Which version of the project should I use?

Thanks for advice.