Sorry that it’s taken me so long to come back around to this. With the pace at which Dorico is developing at the moment, it’s difficult for us to guarantee that the appearance of a score will be completely preserved when bringing it forwards into a newer version, though it seems like this project is especially different. If you would like to keep running e.g. Dorico 2.0 in order to keep working on this project without having to redo any of the formatting you’ve previously done, you can do that: you can rename the ‘Dorico 2’ folder in your Program Files folder to e.g. ‘Dorico 2.1’, then run the Dorico 2.0 installer again: it’ll end up installed alongside.
Note, though, that there will be some slight annoyances concerning the fact that the two versions share preferences, and e.g. the new option in 2.1 to show a warning when opening a project last saved in an earlier or later version of Dorico will always be turned on again after you have run Dorico 2.0.