Hardcore mode is a option you will find in the menu while in-game, it will restart all your missions, character, the whole world, this is tho optional, only the restart of character and world is optional, having to restart all mission is a must thing. The player should be max level, completed the main Island before doing the hardcore mode.
When you start your hardcore world a new character has been created, your will have to do all this over again but much much harder. Advanced robots: smarter AI, more damage, faster, durable but gives the player a big amount of loot. Lack of loot: Medkits, stimshots, ammo, grenades, flares all that will be more rare to find and less amount. Less xp: you get less xp from everything thats gives xp, making level-up will be much more harder to do. Health: you will generate less health if damaged, medkits gives less health back. Save: you can only save by fast travel to a safehouse if not you lose all your progress and your stuff and respawn at last Safehouse. Freinds: max 2. LvL: you must be at a certian lvl to use this gun so dont even try to sneak one legendery moller pistol in your stash box. challenges: your will be able to complete challanges that can only be completed in hardcore mode, the rewards can only be optained by complete these challanges the same goes for achievements too.
This hardcore mode is for player who completed the game seeking for a challange! This will put there skills on test. See how hard it can be with out our experimental guns and LMGS. Only the strongest of the strongest shall take on this mighty challange.