Can you upload a save as close as possible to when you can first do one of these, ideally a tutorial? I'm not familiar with how to play this game.

I can.

KH Chain of memories Europe.zip

In the zip there's a save from the beginning of the first level (you have to climb the stairs to enter) and a savestate performing a cardbreak/counterattack (for mgba 0.8-6016-bd87038c9 and my European ROM).

I know the savestate probably won't work, so here you have the instructions to do a cardbreak with the save:

0. Activate OpenGL at any resolution, even x1
1. After loading the save, climb the white stairs and cross the door
2. Touch one of the enemies that appear suddenly to start a battle.
3. Wait for any enemy to activate a card and then press A to use one of yours. The glitch will happen.

(actually a cardbreak is performed after using a card with a higher number than the enemy's or a 0 card)