Both were released together. Basically you play any of then and beat it. Pick up the password and send to the other game. In the second game you pick with password, you will be already know as a Hero of the first game, and you will then start on the events normally. At the end of the second game you will be able to fight the real final boss.
Some addictive games: - Battle city - Game and watch gallery 2 - Tetris DX - Killer instinct - Wario blast
Yes. it's sorta like the password function in the Golden Sun Series, only simpler. You have to write it down.
Alright get these Gameboy games. Castlevania 2 Belmonts revenge, contra alien wars, ninja gaiden shadow, and kid icarus myths and monsters. I played these games when I was 8..... Be cautioned that these games are extremely hard. They are fun but, kids nowadays won't play them because they give up to easily when they see a hard game. Enjoy my suffering from when I was a kid MWHHAHAHAHA.