For some reason, after watching WWDC talks mentioning watchOS in the last few years, I had this image in my mind that almost every version changed everything in how apps are built. I remembered something about native and non-native apps, two different types of app schemes in Xcode, and some diagrams of pieces moving from one box to another, on more than one occasion. This all sounded confusing, and I think that’s one reason why I was discouraged from starting, because I imagined it would make it hard for me to catch up with all of that.
As it turned out, this wasn’t really true.
The only change that could be considered major was the move from watchOS 1.0 to 2.0 – it introduced what’s called native apps (somewhat confusingly – since both kinds of apps are native in the usual sense, that they’re written using ObjC and Swift, and not web technologies or some other kind of emulation). But even that, as I understand, was really a smaller change than it appears (though I won’t know for sure). The general architecture, the way you write Watch apps, everything that’s different than what you’re used to from iOS – this all hasn’t really changed since watchOS 1. What’s changed is mostly that apps are faster, can do more work in the background, and have access to more features and frameworks.