Released versions are different between platforms. I know 1.3, 2.0, 3.5, 4.0, 4.1, 5.0 for Solaris, and 2.0, 2.1, 2.2, 4.0, 4.1, 5.0 for Linux.
Refering "Downloads" of Cluster Server UNIX on Product Support site is easy way to collect release info.
> Are versions 2.0 to 3.5 similar to each other,
> and versions 4.0 to 5.0 similar to each other,
> but the two groups are different ?
Log format is changed on 4.0. For detail, get System Administrator's Guide from support.veritas.com and see them.
> what are the differences between them in terms
> of command line utility outputs and options ?
As Gene said, all versions are similar, but there are some differences.
It's hard to explain briefly.