Rulings
Q1: Do I always have to activate this card's effect when I attack?
No. The effect is voluntary.
Q2: If I have 2 or fewer cards in my deck, can I activate this Digimon’s When Attacking effect?
No, you can't.
Q3: Can I use this card's When Attacking effect to trash 6 cards from the top of my deck and give this card +4000 DP?
No, you can't.
Q4: I attack with this card and activate its When Attacking effect to get +2000 DP. I then unsuspend this card using a card effect and attack again. Can I use the When Attacking effect again to get an additional +2000 DP?
Yes, you can.
Q5: Can I activate this card's inherited effect when I have 2 or less non-Digi-Egg cards in my trash?
No, you can't.
Q6: When using this card's inherited effect to return cards from my trash to the bottom of my deck, is my opponent allowed to check what cards I am returning to my deck?
Yes. Cards in your trash are considered public information, so please let your opponent confirm which cards you're returning to your deck before you do so.
Q7: Can I use this card's inherited effect to return 3 non-Digi-Egg cards to the bottom of my deck but not activate Draw 1?
No, you can't.
Data Sources
Lv.4 Veedramon Zero P-011 P Champion | Vaccine | Mythical Dragon [When Attacking] If you have a blue Tamer， you may trash the top 3 cards of your deck to give this Digimon +2000 DP for the turn. --- Inherited: [When Attacking] You may place 3 non-Digi-Egg cards from your trash at the bottom of your deck in any order to activate <Draw 1>. (Draw 1 card from your deck.)
Lv.4 Veedramon Zero P-011 P
Champion | Vaccine | Mythical Dragon
[When Attacking] If you have a {{Colour|blue}} Tamer, by trashing the top 3 cards of your deck, this Digimon gets +2000 DP for the turn.
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Inherited: [When Attacking] By returning 3 non-Digi-Egg cards from your trash to the bottom of your deck in any order, <Draw 1>.Lv.4 ブイドラモン ゼロ P-011 P 成熟期 | ワクチン種 | 幻竜型 【アタック時】青の自分のテイマーがいるとき、自分のデッキの上から3枚破棄することで、このターンの間、このデジモンのDPを+2000する。 --- Inherited: 【アタック時】自分のトラッシュからデジタマカード以外のカード3枚を、好きな順番でデッキの下に戻すことで、≪1ドロー≫（自分のデッキからカードを1枚引く）。