As explained, using About in menus, or looking at the title. Harder ways are by looking at certain versions of Workbench and other libraries, with someone that can tell you what are the most recent versions (e.g. Workbench and Kickstart library).
If I do remember correctly, SAM 440 came with Update 1 CD, so yes, you would need to download all archives and install them correctly from Hyperion website. Good news is after Update 6, you will have an automatic updates set.
Boy we gonna love that OS 4.2 CD once its out for fresh installs and reinstalls