Q1: What happens if an opponent's Digimon that isn't affected by effects is chosen for this card's On Play When Digivolving effect?
Digimon that aren't affected by effects aren't affected by this card's On Play When Digivolving effect. Because this effect didn't delete, you can process the part of the effect after "if this effect didn't delete."
Lv.5 Lucemon: Chaos Mode BT18-082 SR Ultimate | Virus | Demon Lord/Seven Great Demon Lords [Digivolve] [Lucemon]: Cost 6 [On Play] [When Digivolving] Your opponent may delete 1 of their Digimon or Tamers. If this effect didn't delete, <Recovery +1 ≪Deck≫> and trash your opponent's top security card. [All Turns] [Once Per Turn] When this Digimon would leave the battle area, by trashing your bottom security card, it doesn't leave.
Lv.5 Lucemon: Chaos Mode BT18-082 SR Ultimate | Virus | Demon Lord/Seven Great Demon Lords [Digivolve] [Lucemon]: Cost 6 [On Play] [When Digivolving] Your opponent may delete 1 of their Digimon or Tamers. If this effect didn't delete, <Recovery +1 ≪Deck≫> and trash your opponent's top security card. [All Turns] [Once Per Turn] When this Digimon would leave the battle area, by trashing your bottom security card, it doesn't leave.
Lv.5 Lucemon: Chaos Mode BT18-082 SR Ultimate | Virus | Demon Lord/Seven Great Demon Lords [Digivolve] [Lucemon]: Cost 6 [On Play] [When Digivolving] Your opponent may delete 1 of their Digimon or Tamers. If this effect didn't delete, <Recovery +1 (Deck)> and trash the top card of your opponent's security stack. [All Turns] [Once Per Turn] When this Digimon would leave the battle area, by trashing the bottom card of your security stack, it doesn't leave.
Lv.5 ルーチェモン:フォールダウンモード BT18-082 SR 完全体 | ウィルス種 | 魔王型/七大魔王 「ルーチェモン」:コスト6 【登場時】【進化時】相手は自身のデジモン/テイマー1体を消滅できる。この効果で消滅しなかったなら、≪リカバリー+1《デッキ》≫し、相手のセキュリティを上から1枚破棄する。 【お互いのターン】[ターンに1回]このデジモンがバトルエリアを離れるとき、自分のセキュリティを下から1枚破棄することで、離れない。