Is Sibelius Ultimate compatible with earlier versions of Sibelius?

Sibelius can open and save as Sibelius 1, 2, 3, 4, 5, 6, 7, 7.5, 8 and Ultimate files.

What are the PC and MAC system requirements?

Below you will find the recommended minimum requirements:

Windows 64-bit Windows 7 (SP1 or later), Windows 8.1 (not Windows RT) or Windows 10, 1+ GB of RAM, 1 GB hard disk space for Sibelius software only, Internet connection required for software download and activation

Mac Mac OS X 10.12 or 10.13, 10.14, 10.15, 11.0, 1+ GB of RAM 1 GB hard disk space for Sibelius software only, Internet connection required for software download and activation.

If using the Sibelius Sounds library it is recommended to have 8+ GB of RAM, 36 GB hard disk space (SSD preferred) & ASIO compatible audio interface or sound card (Windows only).