Twin Cobra.

 No.  Code  Effect
   1  SANA-BJZY  Start at stage 2
   2  SANA-BNZY  Start at stage 3
   3  SANA-BTZY  Start at stage 4
   4  SANA-BYZY  Start at stage 5
   5  SANA-B2ZY  Start at stage 6
   6  SANA-B6ZY  Start at stage 7
   7  SANA-BAZY  Start at stage 8
   8  AEVA-BA9C  Start with 1 life
   9  CAVA-BA9C  Start with 10 lives
 10  EYVA-BA9C  Start with 25 lives
 11  LAVA-BA9C  Start with 50 lives
 12  XEVA-BA9C  Start with 99 lives
 13  TEYT-AEZ4  Infinite lives
 14  AEVA-AAFY  Start turns with 1 bomb instead of 3
 15  AYVA-AAFY  Start turns with 5 bombs instead of 3
 16  A6VA-AAFY  Start turns with 7 bombs instead of 3  
 17  AJYA-AA5R  Infinite bombs
 18  9TVA-BCFG + AEVA-AAFJ  Start turns with green weaponry
 19  9TVA-BCFG + AJVA-AAFJ  Start turns with blue weaponry
 20  9TVA-BCFG + ANVA-AAFJ  Start turns with yellow weaponry
 21  9TVA-BCFN + AJVA-AAFR  Start turns with double power boost
 22  9TVA-BCFN + ATVA-AAFR    Start turns with triple power boost
 23  AT7T-AA8T S  pick-up worth nothing
 24  HE7T-BJ0T  S pick-up gives 2x power
 25  HE7T-BJ1T  Bomb pick-up adds 2 bombs
 26  HE7T-BN1T  Bomb pick-up adds 3 bombs
 27  HAVA-AE0L  Keep P pick-ups after losing a life
 28  9V6T-BGBE + AF6T-AABG  Start with 1 credit
 29  9V6T-BGBE + AZ6T-AABG  Start with 5 credits
 30  9V6T-BGBE + CB6T-AABG  Start with 10 credits
 31  9V6T-BGBE + EZ6T-AABG  Start with 25 credits
 32  9V6T-BGBE + LB6T-AABG  Start with 50 credits
 33  9V6T-BGBE + XF6T-AABG  Start with 99 credits
 34  JF6T-AEY6  Infinite credits