To enable level select, go to the Passwords screen and enter this code: NTTTTT.
At the Password screen, enter: MFKRPH
Level 2: PBBQBB Level 3: QBCQBB Level 4: SBFQBB Level 5: DBKQBB Level 6: NBTQBB Level 7: PCTQBB Level 8: RFTQBB Level 9: CKTQBB Level 10: MTTQBB