There are indeed 2
main versions. you've got Chrome OS, and Chromium OS.
Chrome OS is the version Google puts on all their Chromebook and Chromeboxes. it includes all copyrighted thingd they've paid for, like mp3,flash... to give you the browser experience you would've on a normal pc.
and Chromium OS is the Open Source type. it doesn't include all these copyrighted things. it's just for browsing the web, and testing purposes.
but there are different versions of Chromium OS, there isn't a standard Chromium OS build, it's just the source code they released. so there are a few developers which made their own version. like Hexxeh and arnoldthebat, you can find thier builds here:
http://chromeos.hexxeh.net/ and
http://arnoldthebat.co.uk
i can't answer those other questions, but i hope i at least helped a little bit.
and good luck with your bachelor!