Is it possible to change Mog from the other moogles sprite ?

To the point if I make Mog say and old man the other moogles stay as moogles .
Also is it possible to take away the option of changing a characters name ?

Taking away the option to name a character is a simple event hack. You just have to find the part of the code where the name change screen appears in the event script and FD it out.

The other change is pretty simple for the most part if you are okay with giving him Banon's sprite or something (povided no nasty issues arise on shop screens or something). Then you just have to assign Banon's sprite to him through event coding. If you want him to have a generic old guy's sprite, you'll have to either replace another character or use Edrin's method to expand the number of sprite sheets so that he can use one in battle.

What programs would I need to do this !!!

You would need a hex editor such as WindHex. Look in the Tools section. You'd probably also want to follow xJCSx's tutorial on how to do event editing. Edrin made some sort of tutorial for expanding the number of sprite sheets, I think, but it is probably quite involved. That wouldn't be an undertaking to jump into lightly, I bet.

You'll also want the FF6 Event Script, which is probably not hard to find, so I won't bother linking you to it.