Is there any way to catch Arceus in any game without events?

Question

They always let some Pokemon be caught in different games... but what about this Fiendish Legendary?

Answer 1

There are a few ways to catch an Arceus in the main series games.

1. After completing the first 26 missions and catching every non-Mythical Pokemon in Legends: Arceus, the player may go to the Hall of Origin to catch Arceus.
2. If the Nintendo Switch has save data from Legends: Arceus with all missions completed, Brilliant Diamond and Shining Pearl will allow the player to visit the Hall of Origin after entering the Hall of Fame.

You can still get an Arceus in Gen 4 by using the DNS Exploit. To the best of my knowledge, this guide still works perfectly well. In addition, tweaking into the Hall of Origin or somehow obtaining the Azure Flute will allow you to catch Arceus, even though it was technically unreleased.

Arceus (Bulbapedia)

Answer 2

No

Simple as that.