Speaking strictly to the 6 connected cells in series (at the bottom), and without regard to the rest of the circuit, the important thing to note is that the subsection there is in effect, it’s own compete circuit.
The 3 “bulbs” (I, N, and G) comprise what’s referred to as a series-parallel circuit. With I being the series component, and N and G comprising the parallel portion.
The orientation of the “external” connection points of the batteries has no effect (because a traditional bulb has no polarity, though LED’s do), the importance lies in the fact that there’s still a difference in potential, which creates the circuit (in simplest terms, one end is still going to be more positive than the other end). I would burn brightest, with N and G splitting the other portion of the available power.
Once the switch is thrown, then polarity and voltages become considerably more important. 
