Yes, you can hack ROMs. You do this by using specific programs you can get here.
http://wahackpokemon.com/en/
Go to the download section and find the tools for your specific platform.
Hacks are distributed as patches, which you apply to the original roms. You get the original roms from your cartridge using a special tool.
You have to have a GBA Roms.
No. It doesn't exist but you can try and download a hacked version or even hack it yourself from a DS
Download Virtual Boy Advance and then download the roms for the Pokemon games.
Go to wah.studiopokemon.com and it's in +Hack Roms.
you can use advanced text which u can download from whack a hack.
If your asking to have no Pokemon in your party, NOT POSSIBLE UNLESS YOU HACK.
You cant, but you can hack the Pokemon you want into the game.
If you're talking about the GBA Cartridge, as in the actual game, no. If you mean ROMs, no, but it is illegal to sell them.
A rom is a downloadable game you can play on your PC for free but it is Illegal. Pokemon is one of the most downloadable game for Ds roms
to hack different games you need different kinds of tools. You can hack NDS, VBA, and GBC roms. For hacking tools go to the link below: http://wahackpokemon.com/en/download/tools-gba
Moemon is a hack for FireRed and Emerald roms.