Beat the game in Normal mode to unlock it. This goes for all Prototype games on all systems.
Hard Mode - Beat the game on Normal mode.
Easy+ and normal+
Mercer keeps all his ep, woi and abilities acquired when you start a new game+(easy and normal)
Easy+ - Beat the game on easy or Normal
Normal+ - Beat the game on Normal
Start a New Game Plus on a different difficulty
After unlocking the New Game Plus option for Easy Mode or Normal Mode, it is possible to start a new game plus on a difficulty setting for which it has not been unlocked. To do this, under New Game, select Easy plus or Normal plus, whichever is applicable. Instead of saving as prompted however, press circle to back out of your selection, and then select a difficulty for which the New Game plus has not been unlocked. Save the data when prompted to begin the game. You will begin the game with New Game plus status, without having unlocked it for the corresponding difficulty setting.
Unlock body surfing ability
From the main menu, select extras and go to cheats.
Right, Right, Left, Down, Up, Up, Up, Down - unlock body surfing ability
Unlockable How to Unlock Au (Silver) Achieve a rating of gold or better in all events Brain Trust (Bronze) Complete all consume events Cleanup (Bronze) Kill 15 characters with a single whipfist attack Endless Hunger (Silver) Consume 200 characters to boost your health Evolutionary step (Bronze) Use the upgrade menu to acquire an upgrade Gunning (Bronze) Destroy 20 helicopters in a single helicopter flight Half-Truths (Bronze) Complete a mission without causing a single military alert Hard To Kill (Gold) Complete story mode in any difficulty without dying Hope (Bronze) Discover the truth behind Hope, Idaho through the Web of Intrigue. In Plain Sight (Bronze) Evade 10 strike teams In The Web (Bronze) Consume 50 web targets Infiltrator (Bronze) Infiltrate 10 military bases disguised as a commander It’s Him! (Bronze) Patsy 5 military personnel Mankind is your mask (Silver) Complete 3 missions without causing a single military alert Misconception (Bronze) Destroy 25 infected water towers before they hatch Nice Guy (Silver) Complete the game while consuming 10 civilians or fewer Origin (Bronze) Discover the history of Elizabeth Greene through the Web of Intrigue. Platinum Trophy Collect all other trophies Polymath (Silver) Collect all hint collectibles scattered across New York City Pt (Gold) Achieve a platinum medal in all events Repossession (Bronze) Seize 50 vehicles from enemy hands Return Fire (Bronze) Catch any object tossed by a hydra; and throw it back Revenge Revisited (Gold) Complete story mode on hard difficulty Self-Deception (Bronze) Discover what happened to Alex Mercer through the web of intrigue SME (Bronze) Gain the ability to drive and fly all vehicles Speed Bumps (Bronze) Run over 500 characters in a single tank Streetwise (Silver) Collect all landmark collectibles scattered across New York City Surface-To-Air (Bronze) Shoot down 50 helicopters while driving armor The butcher (Silver) Kill 50 characters in 5 seconds The Cleaner (Silver) Destroy 10 military bases or infected hives in New York City The First Thread (Bronze) Unlock the web of intrigue Threat Elevated (Bronze) Destroy 25 strike teams Trail Of Corpses (Silver) Kill 53,596 infected Unnatural Selection (Silver) Acquire all available upgrades Web Of Knowledge (Gold) Acquire all nodes of the web of intrigue Wrecking Yard (Bronze) Destroy 2,000 Vehicles