I did some testing to see if other Pokémon can be transferred. And gen 3 pokemon you can’t with the exception of the event deoxys and some of the gen 2 pokemon. Not even hatched ones like my duskull.
And I can’t use my favorite ones from 4KIDS. Also this is the yugioh neuron app for anyone curious.
I’m curious has anyone done the glitch to jump over the wall early game? I sure did and open a few treasure chests. I then transfer my save data from the demo to the full game. I checked 3 different lists online and obtained all I could from the shrine of life and blue treasure chests. I think you might have to start NG+ or a new game if you want to collect the last piece if I’m not mistaken.