

Q1: Can this card be used with an effect that uses an Option card with Huckmon in its text?
Yes, it can. "Text" references the entire card, so it refers to any card with the specified word or icon printed on it.
Q2: What kind of card does "a card with X in its text" refer to?
It refers to a card that contains the specified text or icon in its name, traits, effects, inherited effects, (Rule), digivolve requirements, DNA Digivolve, DigiXros requirements, Burst Digivolve, App Fusion, Link, or Assembly requirements. For example, "a card with Knightmon in its text" would include cards with the name DarkKnightmon and cards with the text Knightmon in their effects.
Q3: All of my Digimon are currently getting -5000 DP, and I use this card's Main effect to play a Digimon with 5000 DP or less. At this time, is the played Digimon deleted before the portion of the effect that follows "Then" is processed?
No, it is not immediately deleted at this point in time. All activated effects are resolved, after which a rule check occurs. At that point in time, all Digimon with 0 DP are deleted simultaneously.
Q4: I used Divine Pierce (Awakened) to play Sistermon Blanc which has an On Play effect. Afterwards, if I Arts Digivolve that Sistermon Blanc into this card, can I activate that Digimon's On Play effect?
No, you can't activate it. It has lost its On Play effect before it can be activated, so the On Play effect can't be activated.
Sistermon Blanc (Awakened) EX13-065 R Rookie | Vaccine | Puppet <Decode ([Sistermon Blanc])> <Guard> (When any of your other Digimon would leave the battle area by your opponent's effects, by deleting this Digimon, they don't leave.) ---
Sistermon Blanc (Awakened) EX13-065 R Rookie | Vaccine | Puppet [Digivolve] [Sistermon Blanc]: Cost 0/Lv.2 w/[Huckmon] in text: Cost 1 <Decode ([Sistermon Blanc])> <Guard> (When any of your other Digimon would leave the battle area by your opponent's effects, by deleting this Digimon, they don't leave.) --- -
Sistermon Blanc (Awakened) EX13-065 R
rookie | Vaccine | Puppet
[Digivolve] [Sistermon Blanc]: Cost 0
{{DigivolveFromSupports|1|2|Huckmon}}
<Decode ([Sistermon Blanc])>
<Guard>
---
[Main] You may play 1 play cost 4 or lower card with [Sistermon] in its name from your hand or trash without paying the cost. Then, to 1 of your opponent's Digimon, give -3000 DP for the turn for each of your Digimon.シスタモン ブラン(覚醒) EX13-065 R 成長期 | ワクチン種 | パペット型 ≪デコード《「シスタモン ブラン」》≫≪守護≫(他の自分のデジモンが相手の効果でバトルエリアを離れるとき、このデジモンを消滅させることで、離れない) ---