4 official rulings from Bandai, last ruled Nov 1, 2024. Straight answers to how this card actually resolves.

When I use this card's effect to digivolve it into a yellow Digimon card with the [Vaccine] in my security stack, can it digivolve regardless of its digivolution requirements?
No, this card's effect does not allow ignoring digivolution requirements, so you can only digivolve into a card that meets the digivolution requirements.
Ruled Mar 28, 2024
Can I use an effect that digivolves my Digimon to digivolve this card into a security card with the [Vaccine]?
No, you can't.
Ruled Mar 28, 2024
I have a Digimon in play with this card in its digivolution cards. [BT1-087]/[T.K. Takaishi]’s effect adds a yellow card from my security stack to my hand, and adds a card to my security stack. The number of cards in my security stack ultimately remained the same, but can I still gain 1 memory from this card’s inherited effect?
Yes. added a card to your security, so you gain 1 memory.
Ruled Mar 28, 2024
I used this card's <Start Your Main> effect to digivolve from a security card, then place a card from my hand at the bottom of the security stack. Do "when a card is added to the security stack" and "when a card is removed from the security stack" effects trigger simultaneously at such times?
Yes, they trigger simultaneously.
Ruled Nov 1, 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.