At the main menu, press Y, R, Y, X, Y, R, X, L, X(3), Y. Note: This also unlocks The Greatest Escape mode.
Pause the game with a gun and health kit in your inventory, then press Y, X, L, R, L, R, X, Y, L, Y(2), R. If you entered the code correctly, a message will appear.
At the main menu, press L(2), Y, X(2), R(2), Y(2), X, L, R. If you entered the code correctly, a message will appear.
Successfully complete the game to unlock the "The Greatest Escape" option. This allows any level to be played with a time limit.
Once you have sneaked past the Kommandant, go to the hut with the timetable. There will be a guard next to it. If you pick it up, the guards will shoot you. Instead, go into the room behind the guard. Turn off the radio and he will leave the timetable. Run into the timetable room and pick it up, then go back inside the camp.
Once you have the key, go to the room before the first class section. Use the key to open the silver barred door to your right. You will get weapons. Then, get on top of the train by climbing the ladder. There will be guards on top of the train. Shoot everyone and go down every ladder, as you will get swarmed by guards on top. When you go down the ladder, they come to you and you can kill them all. Once they are all dead, you can run to where you hid Blythe. Go to the jump off point and run through the door.
At any time, if you get stuck on an objective or have no idea where to go next, bring up your notebook. This brings up your notebook, and tells you exactly where to go and what to do. Use its knowledge often.
During missions, you can only save a certain number of times. The amount of saves you get depends on the mission. Make sure to only save after you clear a major obstacle or objective. If you save too much, it will not let you save anymore and this can cause trouble if you get caught frequently.
Before you finish mission 2 with MacDonald, make sure you are wearing the goon uniform. Slide down the zipline to end the mission. When the mission 3 starts, you should be wearing the goon uniform. This will enable you to easily race to the hut in front of you to answer the phone, and prevent the mountain forces from hearing about you in advance. You can now easily kill the first few guards on the mountain in disguise. However, make sure no other guard sees you killing them. The disguise works until you have to past the two guards near the spotlight.
Once you start, move quickly to the barn in front of you. Once there, do not bother with crawling through the hole in the wall. While outside, follow the guard that is walking around, but do not attack him. Use the first chance you get to go into the barn he is guarding and climb the ladder. Once there, slowly approach the guard and shock him until he dies. Once this is done, turn around and pick up the gun and ammunition. Turn around and talk to the people. After that, pull out the gun and kill the guard patrolling the barn. Next, run out the large doors and turn to the left. Follow that until you get to the point to where you have to kill the four men. Once done, go to the roadblock, then go to the booth. However, go outside the booth and pick up the detonator and other items. Turn around and go down the street. Kill all the men. Go into every building to pick up all the ammunition and guns. When you need to use a health pack, use it. Once at the bridge, place the dynamite and go left to the building that they tell you to go to. Once up on top, place the detonator, but do not push it until the clock-like timer is all most out of time, or just when the front car is on the bridge. After that, slowly kill everyone, one by one. Once again, go into every building you can to get the rocket launcher. Once everyone is dead and you are done, follow the red arrow until you get the item you are looking for.
While you are driving the tank, you encounter another tank. You cannot fight; park somewhere safe and run into the house with the stairs. Go to one of the levers and pull it. You will see a train appear and hit the tank, clearing the path for you.