I know you have no idea who I am, but that's irrelevant.
Anyways, I noticed you were talking to Doesn't lately, saying that you recently learned how to do ASM hacking. I was wondering what tutorial(s) you used to learn it. I tried to learn it a while ago but didn't succeed because the special VBA emulator that lets you see the game's data as you play wasn't working on my computer for some reason.
The best way to test what you've learned is to apply it in practice, in my opinion. Go try to do something interesting with your ROM that requires ASM- the most reasonable task would probably be to implement a custom ability.
Did you expand the habitat data? I'm not sure what's causing your issue but that's the only thing I can think of- if something isn't in the habitat tables the game just displays an arbitrary entry when you catch it. They're documented for English FR here: http://www.pokecommunity.com/showpost.php?p=6263014&postcount=75
Ah, that's sensible! Haha I have an alternate account with unusual characters that I log into using Chrome's incognito mode so I have to c&p every time. Such a pain. xD; Pretty characters are so much fun though. :D
In the English version, there's a function at x104AB0 that manages the pokedex flags. Given an species in r0 and a value in r1, the function either checks or sets a caught or seen flag. The function begins with 0C 20 96 E2 30 31 00 03 0A 4A 91 8D 80 20 40 00, and exists in Japanese Fire Red- I suspect it also exists in the French version. If it does, all of the adjustments made towards fixing the flags will be done here- everything else is just limiters.
The solution I used was to apply JPAN's save block hack, which frees up the help menu RAM and writes it to the save- thus I repointed the Caught/Seen flags to that area. The hack in question is here: http://www.pokecommunity.com/showpost.php?p=6993092&postcount=206. It would probably be a hassle to port to a French ROM however, due to differences in both the ROM, RAM, and quite possibly save structure- I have an alternative solution in mind though.
For whatever reason, the game keeps three sets of Seen flags, which you'll be able to find by looking through the function I mentioned. Provided you do not need more than 784 dex entires, you might be able to repurpose two of these sets to function as the Seen and Caught flags for the new mons.
It's funny how American hackers speak English well but can't spell. People who speak other languages like you spell perfectly. I don't get it :D
Anyway, DoesntKnowHowToPlay found a way to do it, but she's not on at the same time as me usually.