Thanks for answering! The issue is that I still don't know which of the hacks I want to play. I have already played and cleared World Link and Another World, which leaves Puppet Play Enhanced I guess... Also, I'm not clearly sure if there are new hacks or which are the popular ones, that was one of the points I wanted to ask you. About the header part, I did some google'ing and well, it seems like a header issue as you said, but I don't know how that works...
There's
Purple by Agastya (Basically Pokemon Emerald),
Unnamed by Doesnt (same as Fire Red, but has DDC cast and higher overall difficulty),
Blue (also the same as Fire Red, but with more variety with regards to early-game wilds and few roadblocks), and
Tweaked by Neotornado (more 1.5 based, but has a Physical/Special split and Fairy typing).
Touhoumon Cirno is also a possibility. And that just about covers the noteworthy English variants. I can refer you to some Japanese ones as well, if you're interested...
All of them work on my PSP (although I use gPSP-mod instead of gPSP-J).
[inspoiler]Now if only Faith and Prayer could be ported to PSP...[/inspoiler]
[inspoiler]My own game is trash, as well as incomplete and incompatible with PSP, so don't bother.[/inspoiler]