I came here to address a similar issue. I bought the Pro version for PC but am happy enough with the free version for iPad and Android. However, it looks like while I can sync to Google Drive with my PC version, the resulting v4_database file can't then be imported by the other devices from the same Google Drive. Is that correct? So I can "one button sync" to back up my PC but if I want to export-import I need to export from Diarium PC (Pro) into the same folder. Is that right? Or is there a compatibility issue?
It would be nice if the "regular" Diarium could natively read the database files. If I used export/import would it work? Would I lose any extra stuff added in Pro?