Yes there is such a game called Dragon Quest 4. The full name is Dragon Quest 4: Chapters of the Chosen, but in the EU, since it was the first DQ game released, they dropped the '4'. The game plays as a series of chapters, each featuring different characters. It's only in the later ones you meet the game's true hero, and the characters become his companions on his quest.
No, Dragon Quest IX is exclusively a DS title.
There have been no plans announced to port Dragon Quest VIII to the DS.
Dragon Quest X will be on Wii (and Wii U), not DS. There is no official release date yet.
You can have three save game files on Dragon Quest V for the DS.
Dragon Quest 9 came out July 11th.
There are currently 6 DS Dragon Quest games. Dragon Quest IV - The Chapters of the Chosen Dragon Quest V - Hand of the Heavenly Bride Dragon Quest VI - Realms of Reverie (Revelation in the US) Dragon Quest IX - Sentinels of the Starry Sky Dragon Quest Monsters: Joker Dragon Quest Heroes - Rocket Slime
The main Dragon Quest games are:Dragon Quest (Famicom)Dragon Quest II - Luminaries of the Legendary Line (Famicom)Dragon Quest III - The Seeds of Salvation (Famicom)Dragon Quest IV - Chapters of the Chosen (Famicom, DS)Dragon Quest V - Hand of the Heavenly Bride (Super Famicom, DS)Dragon Quest VI - Realms of Reverie (Super Famicom, DS)Dragon Quest VII - Fragments of a Forgotten Past (PlayStation, 3DS)Dragon Quest VIII - Journey of the Cursed King (PlayStation 2, 3DS)Dragon Quest IX - Sentinels of the Starry Skies (Nintendo DS)Dragon Quest X - Awakening of the Five Tribes Online (Wii)Dragon Quest XI - In Search of Departed Time (unreleased - PS4, 3DS, Switch)Several of these games were remade and re-released on other consoles and in other countries. There are also many spin-off games of the Dragon Quest series, including Dragon Quest Mobile, Dragon Quest Monsters, and Slime Morimori (Rocket Slime).
It is DS only so you have to get the cartridge.
You can't
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Drawn to Life
To enter Action Replay codes in Dragon Quest IX, you need to have an Action Replay device compatible with the Nintendo DS. Once you have it, connect your Action Replay to your DS and insert the Dragon Quest IX game cartridge. Open the Action Replay menu, find Dragon Quest IX, and select it to enter the cheat code input screen, where you can input or select the desired codes. After entering the codes, save your changes and start the game to activate the cheats.