Rulings
Q1: Does this card's Opponent's Turn effect activate when an opponent's effect trashes one of my Digimon's digivolution cards?
Yes, it does.
Q2: A "trash 2 digivolution cards" effect activates on 1 of my Digimon with 2 or more digivolution cards when this Digimon has only 1 digivolution card. Can I activate this card's Opponent's Turn effect?
Yes, you can. If you do, trash as many of this card's digivolution cards as possible.
Q3: If a "trash 1 digivolution card" effect activates on 2 of my Digimon, can I activate this card's Opponent's Turn effect and trash just this Digimon's digivolution cards?
Yes, you can. If you do, trash the total number of digivolution cards that would have been trashed from each of the Digimon that you replaced with this Digimon.
Q4: If a "Trash 2 digivolution cards" effect activates on 1 of my Digimon with only 1 digivolution card, can I activate this card's Opponent's Turn effect and trash this Digimon's digivolution cards, and if so, how many do I trash?
Trash 2 cards. If this card has 1 or fewer digivolution cards, trash as many as possible.
Q5: A "trash digivolution cards" effect targets one of my Digimon when this Digimon has 0 digivolution cards. Can I activate this card's Opponent's Turn effect?
Yes, you can. If you do while this Digimon has no digivolution cards, digivolution cards will not be trashed. If there are effects that activate when digivolution cards are trashed, such as "By trashing a digivolution card," the effect will not activate because digivolution cards were not trashed.
Q6: Is it possible for one of my Digimon with 0 digivolution cards to activate an effect that reads "By trashing X of this Digimon's digivolution cards" by way of activating this card's Opponent's Turn effect and trashing those cards from this Digimon?
Yes, it is. If you can trash the number of digivolution cards specified by the effect from this Digimon, your Digimon with 0 digivolution cards can indeed activate such an effect.
Q7: My opponent activates a "Trash the bottom digivolution card of all of your opponent's Digimon" effect. Can I use this card's Opponent's Turn effect to trash just this 1 Digimon's digivolution cards without trashing my other Digimon's digivolution cards?
Yes, you can. If you trash 1 digivolution card for each of your Digimon, you do not have to trash your other Digimon's digivolution cards.
Data Sources
Lv.6 Tactimon BT10-084 C Mega | Data | Wizard/Bagra Army [On Play] You may play 2 level 4 or lower Digimon cards with [Bagra Army] in their traits from your trash without paying their memory costs. All Digimon played by this effect gain <Blocker> until the end of your opponent's turn. [Opponent's Turn] When an effect would trash one of your other Digimon's digivolution cards, you may trash this Digimon's digivolution cards instead.
Lv.6 Tactimon BT10-084 C Mega | Data | Wizard/Bagra Army [On Play] You may play 2 level 4 or lower Digimon cards with [Bagra Army] in their traits from your trash without paying their play costs. The Digimon played by this effect gain <Blocker> until the end of your opponent's turn.[Opponent's Turn] When an effect would trash one of your other Digimon's digivolution cards, you may trash this Digimon's digivolution cards instead.
Lv.6 Tactimon BT10-084 C mega | Data | Wizard/Bagra Army [On Play] You may play 2 level 4 or lower Digimon cards with the [Bagra Army] trait from your trash without paying their memory costs. All Digimon played by this effect gain <Blocker> until the end of your opponent's turn. [Opponent's Turn] When an effect would trash one of your other Digimon's digivolution cards, you may trash this Digimon's digivolution cards with that effect instead.
Lv.6 タクティモン BT10-084 C 究極体 | データ種 | 魔人型/バグラ軍 【登場時】自分のトラッシュから、特徴に「バグラ軍」を持つLv.4以下のデジモンカード2枚をコストを支払わずに登場できる。次の相手ターン終了まで、この効果で登場したデジモン全ては≪ブロッカー≫を得る。 【相手のターン】効果で他の自分のデジモンの進化元を破棄するとき、代わりにこのデジモンの進化元を破棄できる。