Bonus X missions
Successfully complete the game to unlock the bonus X missions in Challenge mode. Completing each X mission unlocks the next mission in the series, in the following order:

X1: Kyriaki
X2: Deftera
X3: Triti
X4: Tetarti
X5: Pempti
X6: Parakevi
X7: Savato

Defusing the bomb
When you are defusing the bomb, take your time. After you are told to pull out the triggers, you do not have to worry about the water anymore. All you will have to do now is follow the wires coming out of the box that show you the temperature. After that, you must take your time. You have to cut red wires and if you touch the white you will lose. Once you cut all the red wires, you will get the operation successful message.