Reach one of the game endings
Finish "Hard truth" quest
Complete "Woman in Red Dress" Board Investigation
Finish "Black Stalker" quest
Finish " Kozlov Killing" or " Kozlov Kidnaping" quest
Finish "The truth about NAR's experiments" quest
Finish "Some excuses" quest
Finish "Chain Reaction" quest
Finish "Checkpoint assault" quest
Finish "Big Fish" quest
Complete "Black Stalker" Board Investigation
Finish "A few things from an old hideout" quest
Finish "Weapon transport" quest
Finish "Hardware for real men" quest
Finish "On opposite sides of the barricade" quest
Recruit Olga
Finish "An old friend" quest
Recruit Tarakan
Complete "Web of Lies" Board Investigation
Finish "Hermit" quest
Change your memory for the first time
Finish "Meeting with Tarakan" quest
Finish "Traitor" quest
Complete "Conspiracy" Board Investigation
Recruit Sashko
Gain access to the third tier of base structures
Finish "Old Documents" quest
Finish "A memento from the past" quest
Recruit Mikhail
Gain access to the second tier of structures in the base
Finish "Hacking into NAR servers" quest
Modify any weapon
Find Oliver and convince him to help you
Finish "Power plant" quest