You can play through each difficulty and unlock the achievement for it, playing on Legendary will unlock Hard and Normal Difficulty achievements retroactively without having to play through again
Complete Campaign Mode On Legendary
u have to complete the campaign on any difficulty
No it does not. You have to beat every level.
If you want all the achievements, then play Legendary. If you just want the "Complete Mission #" achievements and the skulls, play on anything other than Easy.
no
You have to complete the campaign on normal difficulty.
EOD Head - You must complete the campaign mode on Legendary. EOD Shoulders - You must complete the 'The Ark' level on Legendary. EOD Body - You must complete the 'Tsavo Highway' level on Legendary.
Complete all challenges from any two zones and then legendary (fifth difficulty level) will be unlocked.
Yes
there is no cheat u have to complete campaign on any difficulty
complete the campaign in ace difficulty
You have to complete every single mission on hard difficulty.