Q1: If I activate this card's All Turns effect when multiples of my other Digimon with Knightmon in their text would leave the battle area by my opponent's effects at the same time, and I place this Digimon as 1 of those Digimon's bottom digivolution card, are all of my other Digimon with Knightmon in their text prevented from leaving the battle area?
No, only the Digimon where this card was placed as the bottom digivolution card is prevented from leaving the battle area.
Lv.4 Maildramon P-154 P Armor Form | Free | Cyborg [All Turns] When any of your Digimon with [Knightmon] in their texts would leave the battle area by your opponent's effects, by placing this Digimon as any of those Digimon's bottom digivolution card, they don't leave. --- Inherited: <Blocker> (This Digimon can block in the blocker timing.)
Lv.4 Maildramon P-154 P Armor Form | Free | Cyborg [All Turns] When any of your other Digimon with [Knightmon] in their texts would leave the battle area by your opponent's effects, by placing this Digimon as any of those Digimon's bottom digivolution card, they don't leave. --- Inherited: <Blocker> (This Digimon can block in the blocker timing.)
Lv.4 Maildramon P-154 P Armor Form | Free | Cyborg [All Turns] When another of your Digimon with [Knightmon] in its text would leave the battle area by an opponent's effect, by placing this Digimon as its bottom digivolution card, it doesn't leave. --- Inherited: <Blocker> (At blocker timing, by suspending this Digimon, it becomes the attack target.)
Lv.4 メイルドラモン P-154 P アーマー体 | フリー | サイボーグ型 【お互いのターン】「ナイトモン」の記述がある他の自分のデジモンが相手の効果でバトルエリアを離れるとき、このデジモンをそのデジモンの進化元の下に置くことで、離れない。 --- Inherited: ≪ブロッカー≫(このデジモンはブロックタイミングでブロックできる)