Codes:

 Training level  SJ5Z
 1 with intro    STRT
 1 without intro DBQ7
 2               FBWC
 3               QP7R
 4               WJTV
 5               RRYB
 6               ZS9P
 7               XJSN
 8               CGDM
 9               TJ1F
 10              GSG3
 11              BMHS
 12              Y4DJ
 13              HCKD
 14              NRLF
 15              J6BZ
 16              MJXG
 17              K3CH
 18              L8VJ
 19              PBKT
 20              TNLQ
 End             L2RP

 And for the CD version:

 Intro      :  STRT
 Level  1   :  DBQ7
 Level  2   :  FBWC
 Level  3   :  QP7R
 Level  4   :  WJTV
 Level  5   :  L8VJ
 Level  6   :  ZS9P
 Level  7   :  XJSN
 Level  8   :  CGDM
 Level  9   :  PBKT
 Level 10   :  GSG3
 Level 11   :  BMHS
 Level 12   :  Y4OJ
 Level 13   :  TNLQ
 Level 14   :  NRLF
 Level 15   :  MJXG
 Level 16   :  K3CH
 End        :  FMWY