Can anyone tell me if I need to purchase Gold support in order to access and open in Harmony Premium 20, scenes which were created in Harmony Premium 12 and 16?
You can open scenes from earlier versions with newer versions of the software.
You would need Gold Support if you wanted a copy of the older version of the program itself.
So Harmony 20 will open scenes made with versions 12 and 16 of Harmony.
Now things may or may not be absolutely perfect depending on the construction of the older scenes and changes made in the software since then but Harmony 20 should open the files.