To get security armor in Halo 3... all you have to do is get all of the original 49 achievements (you don't need the new mythic or legendary achievements).
Yes, halo 3 mythic is the exact same thing as halo 3 just doesn't have the campaign, also Halo 3 mythic has the new mythic maps included. Online will not change during any gameplay.
you cant you can get more to get the locked armor by getting the new achivments and the mythic map pack. pop
if you buy the halo wars LCE you get a code for the new mythic map pack on Halo 3
* there is no halo 4
play sonic in halo just download and the maps change
Buy halo reacj armor in the startup menu in the armory for credits in online games
For now, no. Although, in the near future a new kind of armor might be introduced, much like Recon armor was in Halo 3.
its something called skills
It is highly suspected that there will be new armor permutations in Halo: CEA because of some screen shots that have been released from official sources.
You get 1 of the 7 vidmaster achievements. Get all seven and you can claim the recon armor.
There are some in Halo 3 ODST.One on Heretic, one on Longshore and one on Citadel.These maps are the new mythic map pack.