theSLAYER

No worries

When Gen 3 was released, it was considered a soft reboot by some fans; Gen 1 or 2 couldn’t connect with Gen 3, (the hardware and games didn’t allow it) and thus couldn't officially transfer up (source: https://bulbapedia.bulbagarden.net/wiki/Trade) Those devices you mentioned aren’t released officially by Nintendo nor The Pokemon Company.

When I say retail cartridge, I meant physical cartridges that could be used with GB or GBC. This event was only distributed to the retail cartridges, not virtual consoles. And no, there’s is no official way to transfer up any retail cartridges for Gen I/II data up to HOME. Any videos you may have seen about uses non-official methods. Non-official methods would render the mons illegal.

There is no official methods to transfer retail carts into VC (which is a prerequisite of transferring this retail event mon into HOME). Even if PKHeX doesn't flag you for its presence in other games, it is still illegal.

There shouldn't be, but perform at your own risk.

Frowned upon, but HOME does not have clone checks (outside of BDSP "cloned mark")

JKSM on 3DS to dump the save. Move the save onto computer for PKHeX usage. Then restore the save to your SD card for your 3DS, and then restore onto your 3DS

To keep things simple, download the wonder card file from here, and use PKHeX to inject it into your save. If you can use PKSM, you can use JKSM to extract the save, for use with PKHeX.

I don’t know how you’re injecting the event into PKSM, are you dragging in the wonder card, or selecting the pokemon from the menu? There’s a total of 19 Dahara Arceus: one for each type + one normal type shiny. If you’re using this wonder card, it should give you the correct Arceus, but if you’re doing some kind of selection, there’s a chance you’re choosing the wrong Arceus.