This is not a four player simultaneous game; only 2 player or 2 players simultaneous. The multitap is used if one or both of the players want to fire an move in independent directions using the d-pad on two controllers at once.
This is the first licensed NES game to be manufactured by another company besides Nintendo. Early on, Nintendo required all licensees to submit their game to Nintendo for manufacturing. Nintendo allowed Acclaim to manufacture their own cartridges this time.