In American versions, the trick is to look at the width of the screen. Versions 1, 2, 3, and 4 all had the classic sized square screen, with icons on the top and bottom and a decorative border on the sides. With the v5/Familitchi and onward, they got rid of the border on the sides and extended the screen, making them what I call "wide-screen tamas". Because of the change in screen size (and the resulting change in animation, but that's a bit more complex than most people care to know about), the v1-v4, or "square-screen", tamas can't connect to the v5 and up tamas. Basically, wide-screen can only connect to wide-screen, and square-screen can only connect to square-screen. (I have one of every version except v4.5 and v5.5, so I've tried every connection I could, trust me.)
Hope it helped!
Pikachi out.