by default the ccustom firmware will require the 2.71 homebrew in the "game" folder and the 1.5 hb in the "game150" folder the folder it is in determins if it is loaded with 2.71 kernal\user mode or 1.50 kernal\user mode as each version has different syscalls and one cant use the other.

as for se version SE-A was the first release by dark_alex which would give you a 2.71 psp with 1.5+2.71 full homebrew call it the "golden firmware" that how i feel about it SE-B was an update for it which added the ability to load iso directly from the Game->memstick menu in the xmb and the SE-B2 was released as a quick update for loading iso from xmb without requiring a umd in the drive.

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