Of course, you need to have access to Level in the Custom Mode Parameters. I don't remember what level it unlocks under, but I know it's a pretty high level. (Level 100 is the last level to unlock something in Streets of Fury, which is Mr. Gomez.)

Level 1: Wong the Giant
1. Level 1-1: Infiltrating the streets (Meet Alias!)
2. Level 1-2: Underground interlude (subway)
3. Level 1-3: Wong is near
Level 2: Jean Bonbeur
4. Level 2-1: You are not alone
5. Level 2-2: Street fight (one plane back alley rumble)
6. Level 2-3: Way too calm... (Meet Jean Bonbeur!)
7. Level 2-4: Blocking is not enough (subway chase)
8. Level 2-5: Chaos
Level 3: Gouri Yayarine
9. Level 3-1: Pantin (parking garage)
10. Level 3-2: Narrow street (two plane business/park rumble)
11. Level 3-3: Fight an army
Level 4: MC Mac Dubois
12. Level 4-1: Bad breaking (Meet Binkman!)
13. Level 4-2: Dance to the music (Meet... that beatboxing guy...)
14. Level 4-3: Hip Hop hideout (subway chase #2)
15. Level 4-4: Hip Hop beating
Level 5: The Big Boss
16. Level 5-1: Fight the suits (Meet the Kendo Stick Bros.!)
17. Level 5-2: Eiffel tower (Meet the elder Kendo Stick Bro!)
18. Level 5-3: Eiffel tower hidden floor

Level 1: MC Mac Dubois
1. Level 1-1: Meet the negociator
2. Level 1-2: Confront MC Mac Dubois
Level 2: Wong the Giant
3. Level 2-1: Heading south
4. Level 2-2: Let it slide
5. Level 2-3: Entering Wong's territory
6. Level 2-4: Tough negociations
Level 3: Jean Bonbeur
7. Level 3-1: They feel no pain
8. Level 3-2: Death corridor
9. Level 3-3: We have honor
10. Level 3-4: I thought Trafalgar square was in London
Level 4: The Big Boss
11. Level 4-1: That guy is dynamite
12. Level 4-2: Is it 4th of july? (Sam I Am joins)
13. Level 4-3: Taking care of the family
14. Level 4-4: An offer you can't refuse (fight Gouri Yayarine)
Level 5: The Big Boss (for realsies)
15. Level 5-1: And this is crazy
16. Level 5-2: The last stand (Mr. Gomez joins)
17. Level 5-3: Fragile alliance (Battle Royale!!!)