life and the prophecy

[mirodunum]

No: HPFGUIDX 111973

I looked for this in the archives since I'm sure it must have been 
done before, but I couldn't find it, so sorry if I'm repeating 
things.  

The prophecy (in OotP) has been bothering me:

(a) if "neither can live while the other survives", what does that 
imply? As far as we know, Harry is alive and will be until at least 
Book 7.  Voldemort got his  body back at the end of book 4; so 
they'll both be alive for two or three years, no?

We gather from Voldemort that he's done something towards making 
himself immortal: how far has he gone down this line?  Presumably his 
aim is to make it so he can't be killed and is fully immortal, but if 
he can't die, is he really alive?  Can his body die, as it did 
before, leaving his mind or soul alive?

(b) "either must die at the hand of the other" - does this mean they 
can't be killed except by each other? If Dumbledore knows or suspects 
this, is that why he didn't attack Voldemort in the ministry of 
magic?  Following on, what would happen if any if the DEs tried to AK 
Harry?  Would he survive it again because if he dies, he must die at 
Voldemort's hand, or is on Voldemort's orders enough?

Unravel the mystery for me!

Mirodunum