Portkey mysteries

[Rebecca Boswell]

No: HPFGUIDX 14095

    I have one question that has been bothering me for a while, and I was
wondering if you guys could help me with it.
    Why would Moody/Crouch have to get Harry to thew Triwizard Cup?
Couldn't be have just thrown Harry something that was a portkey, or knocked
him over the head and sent him to Voldemort?  And how could Harry get back
to Hogwarts if Portkeys have specific times where they work?

   --Becca