Please don't question my curiosity.
Yes, you can.
Later, after the player has visited the Sinjoh Ruins with either an event Arceus or an Arceus caught in the Hall of Origin, they may take the other Arceus to the Ruins of Alph and be transported back to the Sinjoh Ruins. During this second trip, Cynthia has returned to Sinnoh, and the player can go to the Mystri Stage to obtain one of the dragons they had not previously obtained. The event may only be activated twice, by using one of each type of Arceus.
Source: Bulbapedia
