

Q1: Can I use this card's When Attacking effect to digivolve it into a Digimon card with Leomon in its name in my hand regardless of its digivolution requirements?
No, you can’t ignore digivolution requirements when using this effect. You can only digivolve this card into an applicable Digimon card with Leomon in its name.
Lv.4 Liamon EX5-030 C Champion | Vaccine | Holy Beast [When Attacking] This Digimon may digivolve into a Digimon card with [Leomon] in its name in your hand with the digivolution cost reduced by 1. (Rule) Name: Also treated as having [Leomon]. --- [On Deletion] 1 of your opponent's Digimon gets -2000 DP until the end of their turn.
Lv.4 Liamon EX5-030 C Champion | Vaccine | Holy Beast [Digivolve] [Liollmon]/[Elecmon]: Cost 2 [When Attacking] This Digimon may digivolve into a Digimon card with [Leomon] in its name in your hand with the digivolution cost reduced by 1. (Rule) Name: Also treated as having [Leomon]. --- [On Deletion] 1 of your opponent's Digimon gets -2000 DP until the end of their turn.
Lv.4 Liamon EX5-030 C champion | Vaccine | Holy Beast [Digivolve] [Liollmon]/[Elecmon]: Cost 2 [When Attacking] This Digimon may digivolve into a Digimon card with [Leomon] in its name in your hand with the digivolution cost reduced by 1. (Rule) Name: Also treated as having [Leomon]. --- [On Deletion] 1 of your opponent's Digimon gets -2000 DP until the end of their turn.
Lv.4 ライアモン EX5-030 C 成熟期 | ワクチン種 | 聖獣型 【アタック時】このデジモンを自分の手札の名称に「レオモン」を含むデジモンカードに支払う進化コスト-1で進化できる。 <ルール>名称:「レオモン」を含むものとしても扱う。 --- 【消滅時】相手のターン終了まで、相手のデジモン1体をDP-2000。