To play this on a PC or mobile device, you will need an emulator like mGBA (PC) or MyBoy! (Android). Final Verdict
The ability to catch Pokémon from later generations (Sinnoh, Unova, etc.) within the Hoenn region.
Gym leaders with full teams of six and competitive AI.
The safest way to play is to download the .ups or .bps patch file from a reputable community like PokeCommunity or ROMhacking.net , and apply it to a legal backup of your own Pokémon Emerald ROM.
A Pokémon ROM should typically end in .gba . If a site asks you to download an "installer" or an .exe file to play, it is likely malware.
When searching for "free" ROM downloads, you must navigate with caution. Because ROM hacks exist in a legal gray area, they are rarely hosted on official marketplaces.