

Q1: Can I activate a Counter effect and then activate another Counter effect?
No, you can't. Only 1 Counter effect can be activated during 1 attack.
Lv.5 Giromon BT26-055 U Ultimate | Vaccine | Mine/DM/Ver.3 <Fragment《2》> [On Play] [When Digivolving] [Counter] [Once Per Turn] You may place 1 card in your hand face down as this Digimon's bottom digivolution card. Then, you may delete 1 of your Digimon with the [Ver.3] trait and all of your opponent's Digimon with the lowest play cost. --- [All Turns] [Once Per Turn] When this Digimon would leave the battle area, trash your opponent's top security card.
Lv.5 Giromon BT26-055 U Ultimate | Vaccine | Mine/DM/Ver.3 [Digivolve] Lv.4 w/[DM] trait: Cost 3 <Fragment《2》> [On Play] [When Digivolving] [Counter] [Once Per Turn] You may place 1 card in your hand face down as this Digimon's bottom digivolution card. Then, you may delete 1 of your Digimon with the [Ver.3] trait and all of your opponent's Digimon with the lowest play cost. --- [All Turns] [Once Per Turn] When this Digimon would leave the battle area, trash your opponent's top security card.
Lv.5 Giromon BT26-055 U ultimate | Vaccine | Mine/DM/Ver.3 [Digivolve] Lv.4 w/[DM] trait: Cost 3 <Fragment ≪2≫> [On Play] [When Digivolving] [Counter] [Once Per Turn] You may place 1 card in your hand face down as this Digimon's bottom digivolution card. Then, you may delete 1 of your Digimon with the [Ver.3] trait and all of your opponent's Digimon with the lowest play cost. --- [All Turns] [Once Per Turn] When this Digimon would leave the battle area, trash your opponent's top security card.
Lv.5 ギロモン BT26-055 U 完全体 | ワクチン種 | 機雷型/DM/Ver.3 ≪フラグメント《2》≫ 【登場時】【進化時】【カウンター】[ターン1回]自分の手札1枚をこのデジモンの進化元の下に裏向きで置ける。その後、特徴「Ver.3」を持つ自分のデジモン1体と最も登場コストの低い相手のデジモン全てを消滅できる。 --- 【お互いのターン】[ターン1回]このデジモンがバトルエリアを離れるとき、相手のセキュリティを上から1枚破棄する。