Replying to all the Questions you have asked:
Actually you are taking wrong intuition of the problem set.
Here we are building sextuples from the given set only.
for instance: Let N=2 and 2 elements are {2,3}.
so the sextuples generated will be as:
{2,2,2,2,2,2},{2,2,2,2,2,3},{2,2,2,2,3,2},{2,2,2,3,2,2},{2,2,3,2,2,2} . . so & so upto. . . . . {2,2,2,3,3,3},{2,2,3,3,3,3},{2,3,3,3,3,3},{3,3,3,3,3,3}
where general from is {a,b,c,d,e,f}
now, from these sextuples set formed, only 4 of them qualifies as: a*(b+c) = d+(e*f), which you can easily find using pen & paper.
Happy Coding.