Q1: My Digimon attacks and digivolves into this card by an effect during the attack. Can I use this card's When Digivolving effect to attack again?
No, you can't. An attack declaration can't be made during an attack.
Lv.6 Rapidmon (X Antibody) BT16-101 SEC Mega | Vaccine | Holy Warrior/X Antibody [Digivolve] [Rapidmon]: Cost 4 <Armor Purge> [When Digivolving] Suspend all of your opponent's Digimon. Then, this Digimon may attack. [All Turns] While [Rapidmon] or [X Antibody] is in this Digimon's digivolution cards, all of your opponent's suspended Digimon get -4000 DP. [All Turns] [Once Per Turn] When an opponent's Digimon is deleted in battle or by having 0 DP, gain 2 memory.
Lv.6 Rapidmon (X Antibody) BT16-101 SEC Mega | Vaccine | Holy Warrior/X Antibody [Digivolve] [Rapidmon]: Cost 4 <Armor Purge> [When Digivolving] Suspend all of your opponent's Digimon. Then, this Digimon may attack. [All Turns] While [Rapidmon] or [X Antibody] is in this Digimon's digivolution cards, all of your opponent's suspended Digimon get -4000 DP. [All Turns] [Once Per Turn] When an opponent's Digimon is deleted in battle or by having 0 DP, gain 2 memory.
Lv.6 Rapidmon (X Antibody) BT16-101 SEC Mega | Vaccine | Holy Warrior/X Antibody [Digivolve] [Rapidmon]: Cost 4 <Armor Purge> [When Digivolving] Suspend all of your opponent's Digimon. Then, this Digimon may attack. [All Turns] While [Rapidmon] or [X Antibody] is in this Digimon's digivolution cards, all of your opponent's suspended Digimon get -4000 DP. [All Turns] [Once Per Turn] When an opponent's Digimon is deleted in battle or by having 0 DP, gain 2 memory.
Lv.6 ラピッドモンX抗体 BT16-101 SEC 究極体 | ワクチン種 | 聖騎士型/X抗体 「ラピッドモン」:コスト4 ≪アーマー解除≫ 【進化時】相手のデジモン全てをレストさせる。その後、このデジモンでアタックできる。 【お互いのターン】このデジモンの進化元に「ラピッドモン」/「X抗体」がある間、レスト状態の相手のデジモン全てをDP-4000。 【お互いのターン】[ターンに1回]相手のデジモンがバトルかDPが0になって消滅したとき、メモリー+2。