Rulings
Q1: The situation is that the opponent has 2 Digimon. If one of my opponent's Digimon becomes a Digitama Card without DP due to De-Digivolve 2 of this card's On Play and When Digivolving effects, does it satisfy the "if the opponent has 2 or more Digimon" requirement of this effect after that?
Yes, it satisfies. In this situation, even if <De-Digivolving> causes the opponent's Digimon to become a Digitamon card with no DP, it is not trashed until the card's On Play and When Digivolved effects are resolved, and the card is treated as a Digimon. Therefore, the "if there are 2 or more opponent Digimon" condition of this effect is met, and you can return one of your opponent's Digimon of Lv.4 or lower to your hand. After returning it, the Digimon card is trashed. Also, if this effect returns a Digimon card to your hand, the card is placed at the bottom of the Digi-egg Deck.
Q2: The situation is that the opponent has 2 Digimon. If an opponent's Digimon becomes a Tamer by De-Digivolve 1 of this card's On Play When Digivolving effect, does it satisfy the "if the opponent has 2 or more Digimon" requirement of this effect after that?
No, it does not. In this situation, if the opponent's Digimon becomes a Tamer by De-Digivolve, the "if the opponent has 2 or more Digimon" condition of this effect is not met.
Q3: Which card can play from under the tamer by this card's On Deletion effect?
A Digimon card with "Blue Flare" or "Cross Heart" in its trait and play cost 5 or less.
Data Sources
Lv.6 ZeigGreymon BT19-026 R Mega | Virus | Cyborg/Blue Flare [On Play] [When Digivolving] <De-Digivolve 2> 1 of your opponent's Digimon. Then, if your opponent has 2 or more Digimon, return 1 of their level 4 or lower Digimon to the hand. [On Deletion] You may play 1 [Blue Flare] or [Xros Heart] trait Digimon card with a play cost of 5 or less from under your Tamers without paying the cost. Then, <Save>. --- Inherited: [All Turns] This Digimon gets +2000 DP.
Lv.6 ZeigGreymon BT19-026 R Mega | Virus | Cyborg/Blue Flare [On Play] [When Digivolving] <De-Digivolve 2> 1 of your opponent's Digimon. Then, if your opponent has 2 or more Digimon, return 1 of your opponent's level 4 or lower Digimon to the hand. [On Deletion] You may play 1 [Blue Flare] or [Xros Heart] trait trait Digimon card with a play cost of 5 or less from under your Tamers without paying the cost. Then, <Save>. --- Inherited: [All Turns] This Digimon gets +2000 DP.
Lv.6 ジークグレイモン BT19-026 R 究極体 | ウィルス種 | サイボーグ型/ブルーフレア 【登場時】【進化時】相手のデジモン1体を≪退化2≫。その後、相手のデジモンが2体以上なら、Lv.4以下の相手のデジモン1体を手札に戻す。 【消滅時】自分のテイマーの下から、特徴に「ブルーフレア」/「クロスハート」を持つ登場コスト5以下のデジモンカード1枚をコストを支払わずに登場できる。その後、≪セーブ≫。 --- Inherited: 【お互いのターン】このデジモンをDP+2000。