2 official rulings from Bandai, last ruled Mar 28, 2024. Straight answers to how this card actually resolves.

Can I use this card’s <On Play> effect to place a [Ginkakumon Promote] from my trash in this card’s digivolution cards?
No. This card’s <On Play> effect can only be used to place cards whose names match either [Kinkakumon] or [Ginkakumon] exactly, therefore you can't place [Ginkakumon Promote] in digivolution cards.
Ruled Mar 28, 2024
If I have both [Kinkakumon] and [Ginkakumon] in my trash, does this card’s <On Play> effect force me to place both cards in this card’s digivolution cards?
No, "You may place..." means that you can choose if you want to place them as digivolution cards or not. However, if you choose to place, you must place as many digivolution cards as possible. So, if you have both [Kinkakumon] and [Ginkakumon], you can't choose to place only one of them.
Ruled Mar 28, 2024
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Questions and answers are Bandai's official rulings, collected and translated by the DigimonCardGame Wiki community and reused here under CC BY-SA. Card names and card text are © their respective publishers; Combalo is not affiliated with Bandai.