Finale 2014 and PrintMusic 2014 introduced backwards compatibility (to 2012 products only) as a new feature. To open a Finale 2014 file in Finale 2012:
In Finale 2014, 2014.5, or v.25 choose File > Export > Finale 2012. Name and save the file. This will create a copy of your .musx file in the Finale 2012 format (.mus). Open Finale 2012 and open the file normally. If you are using an older version of any Finale notation program (2012 or earlier), these are not directly backward compatible. This means that a later version of Finale, Allegro, PrintMusic, SongWriter or NotePad will always open files created in the same or any earlier version, but an earlier version cannot open files created in a newer version. For example, Finale 2010 can open any file created in Finale 2004, but Finale 2004 cannot open files created in Finale 2010.
While older Finale family notation programs are not directly backward compatible through MUS files, you can use the export MusicXML feature to create files that can be imported in later versions of Finale. MusicXML files created in any version can be opened by any program that can read MusicXML files. In some cases, it may be necessary to convert to an earlier version of MusicXML. This option is new in Finale v.25 (File > Export > MusicXML Preferences).