You need to be more specific on the "Diamond" there are a few emblems that look like Diamonds Here is a link to the list of emblems and how to get them: http://emotionalninja.net/modern-warfare-2-how-to-get-titles-and-emblems/776/2
Challenge: "Free-for-all Victor: I" - Place first, second or third in 3 Free-for-all matches. http://callofduty.wikia.com/wiki/Callsigns For all Titles and Emblems.
You can get them many ways such as leveling up, completing challenges, etc.
I don't know but there is a spotty nerd called Liam crumlish from barnfield south academy
you cant. only by playing certain game modes such as 3rd person team tactical or in private matches go to match settings and change the '3rd person' to on
Only works on regular private matches
im modern warfare 2 if someone kills you and then u kill them back it is called payback. when you get "pay"back off of somebody money falls out of them
to get titles and emblems on modern warfare 2, you have to complete the challenges in the barracks, but for some you have to prestige
Not in Private matches, but you can in normal, online matches
No you don't lose your emblems and titles
Yes you can
You need to be more specific on the "Diamond" there are a few emblems that look like Diamonds Here is a link to the list of emblems and how to get them: http://emotionalninja.net/modern-warfare-2-how-to-get-titles-and-emblems/776/2
No
heres one with emblems and titiles http://www.se7ensins.com/forums/modern-warfare-2-discussion/156442-callsigns-and-emblems-pic-list.html and heres how to get them http://www.se7ensins.com/forums/modern-warfare-2-discussion/156444-callsigns-and-get-them.html
Unlock the challenges for them.
Complete challenges and level up.
Your face thats the answer