In 1997, Nintendo put the first details and screenshots of their next Pocket Monsters game online. It was initially named “Pocket Monsters 2 Gold & Silver”, and was developed for Game Boy and Super Game Boy and was planned for release at the end of the same year.
One of the main points posted was the addition of a skateboard as a secondary transportation method besides the bicycle from the previous games. It was said that the skateboard would allow the player to go to unusual places. Also mentioned in the releases were the integrated RTC (Real Time Clock), additional evolutions for Red/Green/Blue Pokémon, breeding and Pokémon eggs, 100 new Pokémon boosting the total amount to 251, new technical and hidden machines, new attacks, and better in-battle graphics. The game’s communication abilities were also improved, adding trading and fighting between each version and backwards compatibility with R/G/B.
The Pokémon in Pokémon Gold and Silver were just a few of many different designs that Game Freak created. Only 100 new Pokémon were added, and even those often went through redesigns before making it into the final product.”
Info from: http://bulbapedia.bulbagarden.net
The original Starters were Kurusu, Honooguma and Happa (early design for Chikorita).
The Beta Safari Zone is an area programmed into Gold, Silver, and Crystal Versions, which the programmers attempted to remove from the rest of the in-game world by deleting the entrances. It was intended to be located in Fuchsia City, as its Pokemon Red & Blue counterpart was. Although the entrances to the Safari Zone were removed, the warps still exist, so it is possible to enter the area. However, players should not save within the area without a teleporting Pokémon because the exits were fully removed. It’s possible that this zone was not finished because the team did not have enough time.
Thanks to Enricothedark for the contribution! Info from: http://bulbapedia.bulbagarden.net
You can also find a lot of information on the development of the games from Celebi23’s Poket Monsters 2 archive! Credit to “I am Christina Aguilera” from Lost Levels forums for the “Japanese Gameboy Magazine” scans!
Video (from 1:58 to 2:05: POKEMON GOLD BETA):