Regards the "Hammerhead"....I don't know if there are descriptions or rules to support this, but I've always heard the Hammerhead is a vertical line, with a 180 degree yaw turn that takes MORE than 2 wingspans, thus being "flown" through the turn, then a vertical down line.
The STALL Turn is very similar, except manuever descriptions require that the up and down vertical lines are the same track, thus requiring the "turn" at the top to be essentially a pivot, or autorotation about the CG in the Yaw axis. Stall turns carry significant judging downgrades if the pivot uses more than 1 1/2 wingspans.
To the best of my knowledge, all F3A maneuvers like this are STALL turns, and not Hammerheads.