I don't think there's enough variety in that game to split it up really - maybe they could have made it into two or three games with different graphics or something, like on the 15 in 1. but either way I think the 4 in 1 release or some undiscovered version by Rinco came first, then all the 15 in 1 variations. then any plug & play version would have been made after that I guess, if one exists somewhere.
incidentally I just took a look at the Zdog's PCB, there's a smaller one mounted on a larger one, the larger one has "VT03060417-B-02" on it.. maybe 060417 is a date? (ie 17th April 2006). the smaller one seems to be the one with the actual ROM chip and VT03, that one says HZ9979 V2.0.
(theres also a number "HZ0601032 Ver 2.1" on the instruction sheet that comes with it, and the Samuri has HZ0600316 on its intro screen. I guess HZ stands for Hummer-Zechess)
just found a secret in the zdog, if you hold down A, B, select and start on startup you get a screen saying "2006-05-24 HZ0601032 VER 3.8". as far as i know theres nothing like that in the Samuri though.
oh wait, yes there is.
in the Samuri its "2006-05-15 HZ0600316 VER 3.5". you also get a chance to hear the whole menu tune if you do that - ordinarily it doesnt get to play unless you keep moving the cursor around because it'll just reset to the title screen.