need help with EBOOT.pbp, Multi-player with emulators.

[gezegond]

Hi! I need info on 2 separate subjects:
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01: EBOOT.pbp
I have many emulators on my PSP, most of them are just a "EBOOT.pbp" file. I need info on this file. What is it?
To be more percise I want to know if there's a way to decompile one, change something in it and then compile it again into EBOOT.pbp.
The reason I'm asking this is because I want to change how the Emulators look on my XMB, change their XMB background to show the console they're emulating, to get them a little bit more organized...
Also if you have info how to make files that appear on XMB, I would really appreciate it, I know how to make Background and Icon Images, (I made them for some PS1 games I converted to PSP)

Thanks (a lot)!
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02: Multi-player with emulators
I want to know if I can play some games running under emulators multi-player locally via ad-hoc with another PSP that also has those Emulators.

I've heard IRshell lets you play two-player PS1 games, Could you direct me to an article that would show me how? (I don't have IRShell, I'm not sure what it is, (It seems it's a lot of different thing!))

I also have gpsp, it has an ad-hoc section in it's menu, but I don't know how it works, could you tell me how to use it?

If you have any info on other emulators, could you tell me about it? Can you play NES, SNES, Genesis games multi-player?

Thanks!
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PS: Sorry for being so talkative!!

[Qmark]

1.
Pbp-unpacker
http://www.pdc.me.uk/pbp/

[gezegond]

1.
Pbp-unpacker
http://www.pdc.me.uk/pbp/

Thanks.