How do you get Lugia on Pokemon Diamond version without an action replay?

Answer 1

Through normal gameplay you can't but I'll tell you some ways to get a legitimate Lugia.In third generation,if you have the Mystic Ticket,(which you can't get anymore,except through cheating) you can capture it at Naval Rock,then you can migrate it to Pokemon Diamond through the Pal Park.You can also get one by trading with Pokemon XD Gale of Darkness.Purify Shadow Lugia by getting all of the "chambers" in the purification chamber to be a "best circle",then trade it to a third generation game,and migrate it to Pokemon Diamond.Lastly,you can capture one in Pokemon SoulSilver,through normal gameplay,or Pokemon HeartGold in the post-game storyline and trade it over to Pokemon Diamond.

These are the real ways to get a Lugia in Pokemon Diamond.