Rulings
Q1: Can I use this card to digivolve into a Digimon card with a special digivolution costing 3 or less?
Yes, you can.
Q2: Can I use this card to DNA Digivolve into a Digimon card with a DNA Digivolution costing 3 or less?
No. The effect reads “You may digivolve 1 of your Digimon,” so you can’t use it to DNA Digivolve.
Q3: Can I use this card to digivolve one of my Tamers into a Digimon that can digivolve from Tamers?
No. The effect reads “You may digivolve 1 of your Digimon,” so you can’t use it to digivolve a Tamer.
Q4: Can I ignore digivolution requirements when digivolving by the effect of this card, as long as the cost is 3 or less?
No, this card's effect does not allow ignoring digivolution requirements, so you can't ignore digivolution requirements unless some other effect that permits you to do so.
Q5: I have a card in my hand with an effect that reads “1 of your Digimon may digivolve into this card in your hand for a digivolution cost of 3.” Can I use this card’ to digivolve into it?
Yes, you can.
Q6: Can I activate effects that reduce digivolution costs like Digisorption or EX1-071 Win Rate: 60%! to reduce the digivolution cost of a card in my hand from 4 or more to 3 or less, and then use this card to digivolve into it?
No, those effects are only active when the digivolution is taking place, which means they reduce the digivolution cost after a player has announced a digivolution. As such, at the time this card's effect is activated, the digivolution cost hasn't been reduced, and you can't choose the card with this card’s effect.
Q7: I have a Digimon card with multiple digivolution requirements: one with a digivolution cost of 3, and one with a digivolution cost of 4. Can I use this card to digivolve into that Digimon card and apply the requirement with a cost of 4?
No. Even if the card has a digivolution requirement with a cost of 3, if you want to digivolve off the requirement with a cost of 4, you can’t use this card to digivolve.
Data Sources
Digivolution Plug-In S EX2-070 C While you have a Tamer in play, you may use this card without meeting its color requirements.[Main] <Draw 1>. (Draw 1 card from your deck.) Then, you may digivolve 1 of your Digimon into a Digimon card in your hand that can digivolve for a digivolution cost of 3 or less without paying its digivolution cost. --- [Security] Reveal the top 3 cards of your deck. Add 1 Digimon card among them to your hand. Place the remaining cards at the bottom of your deck in any order. Then, add this card to your hand.
Digivolution plug-in S EX2-070 C While you have a Tamer in play, you may use this card without meeting its color requirements.[Main] <Draw 1>. (Draw 1 card from your deck.) Then, you may digivolve 1 of your Digimon into a Digimon card in your hand that can digivolve for a digivolution cost of 3 or less without paying its digivolution cost. --- [Security] Reveal the top 3 cards of your deck. Add 1 Digimon card among them to your hand. Place the remaining cards at the bottom of your deck in any order. Then, add this card to your hand.
Digivolution Plug-In S EX2-070 C While you have a Tamer in play, you may use this card without meeting its color requirements. [Main] <Draw 1>, Then, you may digivolve 1 of your Digimon into a Digimon card in your hand that can digivolve for a digivolution cost of 3 or less without paying its digivolution cost. ---
超進化プラグインS EX2-070 C 自分のテイマーがいる間、このカードは色条件を無視して使用できる。 【メイン】≪1ドロー≫（自分のデッキからカードを1枚引く）。その後、自分のデジモン1体を手札の進化コスト3以下で進化できるデジモンカード1枚にコストを支払わずに進化できる。 --- 【セキュリティ】自分のデッキの上から3枚オープンする。その中のデジモンカード1枚を手札に加える。残ったカードは自分のデッキの下に好きな順番で戻す。その後、このカードを手札に加える。