

Q1: My opponent has a Digimon. Can I meet the "if this effect didn't delete" condition in this card's On Play When Attacking On Deletion effect by not choosing a card to delete?
No, you can't. If your opponent has Digimon, you must choose the card with the lowest play cost among them and delete it.
Q2: My opponent has a Digimon with an effect that prevents deletion. Can I meet the "if this effect didn't delete" condition in this card's On Play When Attacking On Deletion effect by choosing the opponent's Digimon with the effect that prevents deletion?
Yes, you can.
Q3: What kind of card does "a card with X in its text" refer to?
It refers to a card that contains the specified text or icon in its name, traits, effects, inherited effects, (Rule), digivolve requirements, DNA Digivolve, DigiXros requirements, Burst Digivolve, App Fusion, Link, or Assembly requirements. For example, "a card with Knightmon in its text" would include cards with the name DarkKnightmon and cards with the text Knightmon in their effects.
Lv.6 Ghoulmon BT25-076 R Mega | Data | Demon Lord When this card would be played, by deleting 1 of your play cost 11 or lower Digimon with [Negamon] in its digivolution cards and [Negamon] in its text, reduce the cost by the deleted Digimon's play cost. <Rush> <Reboot> <Blocker> [On Play] [When Attacking] [On Deletion] Delete 1 of your opponent's Digimon with the lowest play cost. If this effect didn't delete, trash your opponent's top security card. ---
Lv.6 Ghoulmon BT25-076 R Mega | Data | Demon Lord When this card would be played, by deleting 1 of your play cost 11 or lower Digimon with [Negamon] in its digivolution cards and [Negamon] in its text, reduce the cost by the deleted Digimon's play cost. <Rush> <Reboot> <Blocker> [On Play] [When Attacking] [On Deletion] Delete 1 of your opponent's Digimon with the lowest play cost. If this effect didn't delete, trash your opponent's top security card. --- -
Lv.6 Ghoulmon BT25-076 R mega | Data | Demon Lord When this card would be played, by deleting 1 of your play cost 11 or lower Digimon with [Negamon] in its digivolution cards and [Negamon] in its text, reduce the cost by the deleted Digimon's play cost. <Rush> <Reboot> <Blocker> [On Play] [When Attacking] [On Deletion] Delete 1 of your opponent's Digimon with the lowest play cost. If this effect didn't delete, trash your opponent's top security card.
Lv.6 デスモン BT25-076 R 究極体 | データ種 | 魔王型 このカードが登場するとき、進化元に「ネガーモン」を持つ、「ネガーモン」の記述がある登場コスト11以下の自分のデジモン1体を消滅させることで、消滅させたデジモンの登場コスト分、支払うコストをマイナスする。 ≪速攻≫≪再起動≫≪ブロッカー≫ 【登場時】【アタック時】【消滅時】最も登場コストの低い相手のデジモン1体を消滅させる。この効果で消滅しなかったなら、相手のセキュリティを上から1枚破棄する。 ---