220: Sibelius - opening files in earlier versions

How to open files in earlier versions of Sibelius, Sibelius Student and Sibelius First? Sibelius can open files created or edited in all earlier versions. However, any files created or edited in subsequent versions cannot be opened. For example, Sibelius 6 can open files from anything earlier than Sibelius 7. Likewise, Sibelius 3 can open files from anything earlier than Sibelius 4.