Here are all of the level codes for Easy, Hard and Hardest modes, along with their stage opponent.

(KEY: R=red, B=blue, C=clear, P=purple, G=green, H=has bean, Y=yellow)

Stage Opponent Easy Normal Hard Hardest

2 Frankly RRRH ???? GCYY BBGY
3 Humpty CPCG ???? YPCP GYGC
4 Coconuts RCHY ???? BGCB PPRH
5 Davy Sproket CBBP ???? RPGG GRPB
6 Sqweel CRCP ???? YYCG BPGY
7 Dynamight PYRB ???? PCBB BPGH
8 Grounder YPHB ???? CYHY CPHY
9 Spike YPHB ???? PBBG PGHC
10 Sir Fuzzy Logik RYCH ???? CGRY GBYH
11 Dragon Breath GPBC ???? BYYH GPHR
12 Scratch RHHY ???? GCCB RGHB
13 Dr. Robotnik YHBB ???? HCPH RRCY