Your score rank on the leader board can lower by others getting a higher score than you have.
You get it at rank 45.
you CAN'T
No, multiplayer stats are stored on the server.
Well, he probably plays more than you do, but does worse when he plays. As for you, you don't play as much as him, but you do better than him.
68
You rank up the same speed through out all prestiges
Hacking or killing
kill people, get xp...just like MW2
play team deathmatch and get the top score
By ranking up to a certain level ( i think it is rank 2 or rank 3)
rank resetting is usually your own choice as in becoming prestige
Im guessing you mean the title, you prestige once and get to rank 69