Questions about apparating/portkeys at Hogwarts

[lily_paige_delaney]

No: HPFGUIDX 72998

Here's some weekend homework (LOL!)

According to Hermoine (and Hogwarts, A History)you can't apparate or 
disapparate at Hogwarts - right? 

So how come Dumbledore did it in OoP?  Or was that not apparating 
because he used Fawkes? 

This being the case how come Dumbledore needed to fly to London in 
PS? 

And one more thing, how come you can use a portkey at Hogwarts (GoF & 
OoP)?  Doesn't this defeat the purpose of the protection against 
apparating?  

Anyone??

LPD