Q1: Which can be activated first, the When Digivolving effect of the opponent's Digimon digivolved by the effect or the All Opponent's Turns effect of this card?
Since it is triggered simultaneously, it is activated from the turn player's side of the effect.
Q2: When is the All Turns effect of this card triggered?
Digivolutions are triggered when Digimon are digivolved by effects such as "P-103 Offense Training. The effects of BT4-011 Agunimon, which treats tamers as Lv.3 Digimon, and BT6-060 Deputymon, which ignores digivolution requirements, are not triggered because they do not cause digivolution.
Lv.6 Reapermon BT20-078 U Mega | Virus | Cyborg <Collision> <Blocker> [All Turns] [Once Per Turn] When effects digivolve your opponent's Digimon, <De-Digivolve 1> 1 of your opponent's Digimon. [On Deletion] Delete 1 of your opponent's play cost 4 or lower Digimon or Tamers. (Rule) Trait: Has [Ghost] Type.
Lv.6 Reapermon BT20-078 U Mega | Virus | Cyborg <Collision> (During this Digimon's attack, all of your opponent's Digimon gain <Blocker>, and the opponent blocks if able.) <Blocker> [All Turns] [Once Per Turn] When effects digivolve your opponent's Digimon, <De-Digivolve 1> 1 of your opponent's Digimon. [On Deletion] Delete 1 of your opponent's play cost 4 or lower Digimon or Tamers.
Lv.6 ゴクモン BT20-078 U 究極体 | ウィルス種 | サイボーグ型 ≪衝突≫≪ブロッカー≫ 【お互いのターン】[ターンに1回]相手のデジモンが効果で進化したとき、相手のデジモン1体を≪退化1≫。 【消滅時】登場コスト4以下の相手のデジモン/テイマー1体を消滅させる。 〈ルール〉特徴:タイプ「ゴースト型」を持つ。