dogfight tactic

http://www.youtube.com/watch?v=yjqj1e8t1BE
the maneuver at 4:52 what is it useful for ? why it help evade cannon round from the zero ? and how come a bomber can turn more G than a fighter if they have quite the same speed ?
and here
http://www.youtube.com/watch?v=w4cksG7JoE8
why the zero have to attack head on ?? , why dont they just attack the bomber from behind ??
and btw in Vietnam war the f-4 dont have cannon so they can’t attack Mig fighter at close range so why dont they use hydra 70 or Zuni rocket instead ? , i mean aren’t they just like very big bullet with longer range ?


and why dont they use rocket to attack AA , i mean it seem safer and more accurate than dumb bomb