Q1: When I use this Digimon to attack an opponent's Digimon without digivolution cards, and this card's Your Turn effect deletes that Digimon, what happens to the attack?
Because your opponent's Digimon was the target of the battle and is no longer in play, a battle doesn't occur. However, the counter timing and end of attack timing still exist, therefore any applicable effects will trigger.
Lv.4 Pipismon BT17-064 C Armor Form | Free | Mutant [Digivolve] [Patamon]: Cost 2 <Armor Purge> [When Digivolving] Trash the bottom 2 digivolution cards of 1 of your opponent's Digimon. [Your Turn] When this Digimon attacks an opponent's Digimon with no digivolution cards, delete that Digimon.
Lv.4 Pipismon BT17-064 C Armor Form | Free | Mutant [Digivolve] [Patamon]: Cost 2 <Armor Purge> [When Digivolving] Trash the bottom 2 digivolution cards of 1 of your opponent's Digimon. [Your Turn] When this Digimon attacks an opponent's Digimon with no digivolution cards, delete that Digimon.
Lv.4 Pipismon BT17-064 C Armor Form | Free | Mutant [Digivolve] [Patamon]: Cost 2 <Armor Purge> [When Digivolving] trash the bottom 2 digivolution cards of 1 of your opponent's Digimon. [Your Turn] When this Digimon attacks an opponent's Digimon with no digivolution cards, delete that Digimon.
Lv.4 ピピスモン BT17-064 C アーマー体 | フリー | 突然変異型 「パタモン」:コスト2 ≪アーマー解除≫ 【進化時】相手のデジモン1体の進化元を下から2枚破棄する。 【自分のターン】このデジモンが進化元を持たない相手のデジモンにアタックしたとき、そのデジモンを消滅させる。