It is impossible to get the 10th Prestige moving emblem on Call of Duty: Modern Warfare 2. Infinity Ward made this to catch hackers red handed. That's why you must hack to the get the emblem.
Be 10th prestige
Get to 10th prestige, unlock everything (challenges, emblems, titles, weapon challenges and camos, etc....)
2nd prestige
A new emblem and 10 different custom classes.
You unlock it by getting to 10th Prestige.
In MW2 you get a new emblem and an additional class to use.
By old, do you mean the previous one you had? You can't, unless you quit going into prestige mode, Then you are stuck with the one you have.
Complete all prestige challenges. You must be prestiged at least once.
it is unlocked through prestige challenges and you have to get 100 kills in last stand,alongside this emblem you get a gold title that says 'The Stand'
You need to get "specre VII" I think that's like 1000 AC130 kills, when you get the gloden AC130 title you also get the spinning 10th prestige emblem from modern warfare one.
The highest rank is Prestige 10 at level 70, the emblem is a circle with a skull inside of it.
Not apart from a new title, emblem and the extra custom class slot