There are multiple RPG-7 titles you can unlock in Modern Warfare 2. The first one you will get for getting 500 kills with the RPG-7 (you must have the challenge Prestige Veteran I completed, which I believe means you just have to reach first prestige).
There are also titles available for getting a certain amount of multi-kills with the RPG-7.
For a full list of how to obtain weapon-specific titles, see the link below.
Reach Prestige 1 and Level 69.
Get stabbed by someone who has that title set as his active callsign.
Get to ninth prestige
you have to get 250 kills with melee
No
Use a title that is really hard to get. Such as a 2500 with the spas 12 title Thats what I have ;)
the rpg7
You have to call in two EMP's.
I believe you get it for calling in 50 uavs.
prestige and get to level 35
i dnt know
if you mean the 3 times charm title then go in prestige 3 times