portkey involves aparition which is not possible inside hogwarts.third task happend outside the grounds and hence apparition was possible.but yes,crouch could have made harry touch the portkey before the third task. book6-dumbledore could have easily escaped.why freeze harry when he can use that time to disarm draco?what was dumbledore pleading for when he said please?to leave him or kill him?afterall he doesn't fear death.isn't he the one who said death is the next adenture? i think snape and dumbledore have a plan which will be revealed in book7.