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
Yes you can
Complete challenges and level up.
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
Because, you will actually gain more titles, emblems, and challenges. Why not?
no everything is reset except titles and emblems
You gain titles and emblems by completing certain challenges on multiplayer, check your barracks for the challanges. Here is a list of all the titles and emblems for call of duty modern warfare 2 on the Mordern warfare wiki: http://callofduty.wikia.com/wiki/Callsigns
By completing challenges or raising in rank, same for emblems
Titles - Emblems - Extra Custom Class Slots. Confirmed.
Complete challenges, rank up, prestige, and have fun
You get titles and emblems for doing the majority of challenges you see. I f you look through your challenges you will find that the challenge names are on the titles, some times. there are many apps on the IPhone and I Pod touch that tell you how to get the titles and emblems. I hope this is a good answer for you
You can get them many ways such as leveling up, completing challenges, etc.
From prestiging in modern warfare 2 u get an extra custom class and new emblems and titles.