You can't.
Trade.
You can't you need to get it in the 2009 event or get arceus in trade or mystery gift
u could trade it from someone else or get it from an event
Trade himPokemonknow-it-all:I got an Arceus anyone for Jirachi?
trade with someone who has it
yes
yes.
the only way you can obtain arceus without an action replay is to participate in a Pokemon event. arceus was given out on a movie event. you can also trade with others online on the global terminal or trading friend codes with someone who does have arceus.
Its impossible you need a action replay.
get an arceus of platinum and trade to soulsilver then go to the ruins.
Trade with a friend / trade using GTS. That's the only other way.
You had to have gone to Toys R' Us to receive the event item Azure Flute, or used the Mystery Gift function when it came out. You have missed both. You have to either trade someone for a legit Arceus (Not likely happening), or use codes to obtain the flute.