1) how do u differentiate a ring wraith from the other as they are all the same..izzit through their shriek (different pitching).
Well, unless they're in the "Twilight" state (aka what Frodo saw when he got the Ring on), hard to tell the difference between each of the 8 Ringwraiths in the movie. In the book, maybe they are clothed slightly differently, who knows?
The only one we can tell apart is Witchking of Angmar since his sword and Armor Gauntlets are different from the rest, more decorated. And of course in ROTK, he's the only fellow to wear a War Helm, the Crown of Thorns.
2)who int the world is the mouth of sauron, any history of him before he became the mouth? between him and the witchking..who has the better position next to sauron as in the 2nd in command.
Someone I'm dating right now. ;D You know how sweet he can get with his words and unlike the other 2, he's still a Human.
Okay, okay, Mouth of Sauron, as his name said is the one who "speaks" for Sauron and his Messenger. He's originally a Black Numenorean and said to be the The Lieutenant of the Tower of Barad-dûr.
Between MoS and WK, personally I say WK got more power and 2nd in Command to Sauron since 2nd Age as he not only hem the Army that is to attack Minas Tirith in the 3rd Age and the Lord of the Nazgûl but he have his own stronghold at Minas Morgul (formerly Minis Ithil).
MoS have to share Baradur with Sauron or maybe become its housekeeper.