Pokémon Emerald beta
Unlike other Pokémon games, third version games rarely contain beta information because they are based on an already existing game. Pokémon Emerald is no exception.
Very little was changed in Emerald, in relation to Ruby and Sapphire Versions, with the exception of the Battle Frontier and storyline tweaks to better include the legendaries Kyogre, Groudon, and Rayquaza. While there is no evidence to suggest the storyline was changed seriously, there is evidence that the Battle Frontier was changed slightly in various stages of development, however, these changes are minor and strictly relate almost entirely to building placements and static objects, such as fences.
Kanto and Sevii Islands
It is suggested by extras, such as music and map headers, that Kanto and the Sevii Islands were originally supposed to be accessible somehow, with full maps stored in Emerald's programming. By hacking with the help of a mapping program, it is clear that the headers for each place in the Kanto region are there, though empty with no maps. Most likely, space limitations on the cart disallowed the programmers from adding the regions, or the areas in Hoenn where you can catch Pokémon from those regions were used as a substitute, because of time limitations.
New music
Another proof suggesting an addition of Kanto and the Sevii Islands in Emerald is music from FireRed and LeafGreen. Ruby and Sapphire, the base versions of Emerald, had Johto music in their coding, but Emerald clearly has new Kanto and Sevii Islands music. Kanto and the Sevii Island were most likely scrapped because of limitations, time-wise or for other unknown reasons.
"Special Area"
A new, empty header included with the other empty Kanto and Sevii Islands ones is named "Special Area". There is no actual information on what would have been included in this area, but speculation can show it must have been a new route or section of one of the regions, maybe even allowing the capture of legendaries not in Ruby and Sapphire, with new events.
