Use the following passwords to unlock the corresponding level:
Level 1-1: MG7L4R
Level 1-2: RZHLXM
Level 1-3: WGRLN_
Level 1-4: 3G7L47
Level 2-1: 7ZHLX3
Level 2-2: BBBCBG
Level 2-3: GVLC2B
Level 2-4: LBVCVQ
Level 3-1: QV2CLL
Level 3-2: VBBCBZ
Level 3-3: ZVLC2B
Level 3-4: 2BVCV6
Level 4-1: RL4XGS
Bat Cave Level: BBBBBW
Chinatown Level: BBBBHV
Dock 47 Level: H6T73P
Gotham Rooftops Level: BBBBM6
Gotham Chemicals Level: 5MQZRN
Gotham Sewers Level: 5V2MRN
Boss #1 Level: HLNZXJ