Wow, you have the real cartridge! I like that. ^_^
Sadly, the infinite lives cheat requires a Pro Action Replay cartridge. Truth be told, when it came to the Pro Action Replay code, I actually just simply grabbed it off of Cheatzilla.

Given my methodology of playing SNES games (I usually end up inventing cheats because I'm here to rip SPC set, and thus I intend to make track identification as swift as I possibly can.), I can't measure difficulty on those other two stages.
Luckily, I don't hack games on newer hardware out of respect... plus, it would be mind-boggingly complex because the assembly is that much more complex. And I mainly hack because I go for the soundtrack, and soundtrack preservation is best done with older systems (and for me, easiest to do on the SNES thanks to the format and method of dumping the .spc files... just press dump, and at the next key on event, you get your .spc file). Newer systems? That could cost you an arm and a leg in memory (I'm talking hundreds of megabytes or even gigabytes if it's a reasonably large collection of nothing but audio streams... even MP3 files can go past the hundred MB mark!)... or you might have your mind blown by the file formats it uses (even specific to the game!).
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Just consider me your friendly SPC dumper. Also a bit of a perfectionist (though not too literally)... I make sure my dumps are at the first note. I might even hack away the SFX if needed.
Want a music modifier for a particular SNES game? All you need to do is ask via PM (or you can check out the Music Modifiers topic and post there) and I'll be on the job. ^_^
SPC Set Progress Log