Does Dorico 1 read features of a Dorico 2 file that were part of Dorico 1? (Of course, not new features!)
Does Dorico Elements 2 read all features of a Pro 2 created file? (Or does it “toss out” any features not in Elements?)
Dorico 1.2.10 can indeed open Dorico 2 projects, though exactly what will happen to the file is in many cases undefined: in particular if you have things like slash regions in your Dorico 2 project, if the project is resaved in Dorico 1.2.10 then all of those things will be stripped out.
Dorico Elements 2 reads Dorico Pro projects fully: it doesn’t throw anything away. If the project has more than 12 players, it will open read-only, but it can still be played back and printed, though any changes you make (e.g. to print settings) cannot be saved.
Excellent. I have someone who would rarely use Dorico, but I can send them Pro 2 files which they could use in Elements 2.