

Q1: If I use this card when my opponent has a Digimon with a play cost of 3 and a Tamer with a play cost of 4, can I delete my opponent's Tamer with a play cost of 4 as the Tamer with the lowest play cost?
No, you can't. You must delete the card with the lowest play cost from among all your opponent's Digimon and Tamers for this effect. In the example given in the question, you would delete the Digimon with a play cost of 3 as the card with the lowest play cost.
Ultimate Slicer BT15-097 C [Main] By trashing 1 Digimon card with the [Machine], [Cyborg] or [SoC] trait in your hand, delete 1 of your opponent's Digimon or Tamers with the lowest play cost. --- [Security] Activate this card's [Main] effect.
Ultimate Slicer BT15-097 C [Main] By trashing 1 Digimon card with the [Machine], [Cyborg] or [SoC] trait in your hand, delete 1 of your opponent's Digimon or Tamers with the lowest play cost. --- [Security] Activate this card's [Main] effect.
Ultimate Slicer BT15-097 C [Main] By trashing 1 Digimon card with the [Machine], [Cyborg] or [SoC] trait in your hand, delete 1 of your opponent's Digimon or Tamers with the lowest play cost. --- [Security] Activate this card's [Main] effect.
アルティメットスライサー BT15-097 C 【メイン】自分の手札から、特徴に「マシーン型」/「サイボーグ型」/「SoC」を持つデジモンカード1枚を破棄することで、最も登場コストの低い相手のデジモン/テイマー1体を消滅させる。 --- 【セキュリティ】このカードの【メイン】効果を発揮する。