At the game menu, type SS ADN, then type in these codes:

DARKPOWER               Max Power 
DARKINV                 Invulnerability 
DARK20000               Money Value of 20000 

     There's  another  level  after  the  12th  one  :  Death Blow. To
activate  it, go to the level selection screen and click on the spiral
after you've completed Level 12.

Edit Attributes
     Edit   a   file   called   'units.txt'  in  ..darkreigndarkdeftxt
directory.  Search  for  the Freedom Guard tank settings. Look for the
'Setstrength'  entry  and set your units strength to around 500. There
is  another  field  which sets the price and buildtime set this to say
'50 1'. This will give you cheap tough tanks for around 50 credits and
they will be built really quickly.

Note: You can do the same for the spyder bikes and tank hunters.

     Also  there  is  a  file called 'build.txt' which you can set the
cost  and  increase  the  toughness of your buildings in the same way.
This  works  for all missions up to the 6th one. This is because there
is a dedicated dir and units.txt file for this scenario which you have
to also edit in the same way.

Select Any Mission
     In  the  game directory path 'Dark ReignDarkShell', you'll find a
file  called 'shellcgf.h'. Right click on it and select properties and
then  uncheck  the  'read  only'  box. In this text file you'll find a
section  called  'menu  mission  buttons' under which you will see the
line  '#define BTN_MISSION_COEFFICIENT 150'. Change the value '150' to
the    value    '157'    so    that    the    line    reads   '#define
BTN_MISSION_COEFFICIENT  157'.  Now  when  you run the game, you'll be
able  to select any mission from the dial in the shell by pressing the
new 'cheat' button in the bottom left corner.