Mornin' Danny....I don't know anything about the IMAC laptop. The Mac I'm using is the MacMini. The OS version is 10.6.6 which is the latest version. Whenever upgrades R available I get a notification so I can install them. This is automatic and I presume the same thing applies to any other Mac. U should be able to upgrade to the current version with any Mac U get. Hope this helps. Feel free to email me if U have any other questions.
Bob