Sun Cluster existed from release 2.0 through 3.1. Prior to that it was Solstice HA 1.x and with 3.2, it became Oracle Solaris Cluster. It didn't really find its sea legs until the 2.2 release.
For a brief moment, there was also Sun Cluster PDB specifically for parallel databases.
Sun Cluster 2.2 supported Solaris 2.6, Solaris 7, and Solaris 8.
Like all things Sun Cluster, the nuts and bolts of what works with what gets really hairy.