The total space between the top and bottom gear on 8,9 and 10 speed cassettes is virtually the same. It's the spaces that matter and the shifter will move the derailleur a pre-determined amount per 'click' depending on how many speeds the shifter is. 10 will not shift the chain off a 9 speed cassette, it just won't mesh properly for most of the gears except the first and last. As for the shifter knowing what gear it's in the mechanic (or you) tells it where to start with it's first shift when you set the stop and the tension the cable and the indexing should then hit the rest.

I think my wife's r600 9sp shifters are supposed to be 2/3 compatible on the front. I believe by setting limit screw to only allow for one upshift you effectively eliminate the '3' option.

I've never heard of a branded shimano knock off shifter, but I would believe there may be some '2nds' or refurbs out there. But assuming the link I posted is for the real deal my guess would be they were ordered by a bike manufacturer but not used up in their production run.