Q1: Can I add this card to my hand even if this card's Security effect doesn't delete an opponent's Digimon with 4000 DP or less?
Yes, you can add it to your hand.
Lv.3 Huckmon P-066 P Rookie | Data | Mini Dragon [Security] At the end of the battle, delete 1 of your opponent's Digimon with 4000 DP or less. If no Digimon was deleted by this effect, <Draw 1>. (Draw 1 card from your deck.) Then, add this card to its owner's hand.
Lv.3 Huckmon P-066 P Rookie | Data | Mini Dragon [Security] At the end of the battle, delete 1 of your opponent's Digimon with 4000 DP or less. If you don't delete an opponent's Digimon with this effect, <Draw 1>. (Draw 1 card from your deck.) Then, add this card to its owner's hand.
Lv.3 Huckmon P-066 P Rookie | Data | Mini Dragon [Security] At the end of the battle, delete 1 of your opponent's Digimon with 4000 DP or less. If you don't delete an opponent's Digimon with this effect, <Draw 1>. Then, add this card to its owner's hand.
Lv.3 ハックモン P-066 P 成長期 | データ種 | 小竜型 【セキュリティ】バトル終了時、DP4000以下の相手のデジモン1体を消滅させる。この効果で相手のデジモンが消滅しなかったとき、≪1ドロー≫(自分のデッキからカードを1枚引く)。その後、このカードを手札に加える。