Update: I shot three videos of some tests I've done.
Trading with Pokemon Gold 1997:
https://www.youtube.com/watch?v=28DJOzAmvwsBattling with Pokemon Gold 1997:
https://www.youtube.com/watch?v=IbW8iqQs4EMTrading with Pokemon Blue (Ao):
https://www.youtube.com/watch?v=UmmZ14Tl-30 Trying to battle again crashes the game, so that's interesting. And it turns out the audio glitch was just me hitting Windows on my keyboard causing TGB Dual to freak out. Audio works as intended. Whoops. Thanks everyone for continuing to follow my research.