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

Can I play this Digimon with its <Security> effect even if it loses the battle against the attacking Digimon?
Yes, regardless of the battle's outcome, you get to play this Digimon at the end of the battle.
Ruled Mar 28, 2024
Does this card’s <On Play> effect activate when I play this card with its <Security> effect?
Yes, it does.
Ruled Mar 28, 2024
This card is flipped over during a security check and battles the attacking Digimon as a Security Digimon. Once the battle ends, the attacking Digimon still has security checks remaining. Is this card played off its <Security> effect first, or do I have to wait until my opponent finishes the rest of their security checks? Also, when does this Digimon’s <On Play> effect activate?
This Digimon is played before your opponent's next security check. Likewise, this Digimon’s <On Play> effect activates before your opponent’s next checks.
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.