Rulings
Q1: Can I use this card's effect to play a Digi-Egg in its digivolution cards to my battle area?
No, Digi-Egg cards aren't Digimon cards, so they can't be played with this effect.
Q2: I suspend this card as I declare its attack. If I use its effect to play a Digimon card from its digivolution cards, does that Digimon enter play suspended?
No, it's treated as a separate Digimon, and enters play unsuspended.
Q3: If I use this card's effect to play a Digimon card from its digivolution cards, does that Digimon carry over any effects currently applied to this Digimon?
No, it's treated as a separate Digimon, and doesn't receive any effects that currently apply to the original Digimon.
Q4: If I use this card's effect to play a Digimon card with an On Play effect, does that effect activate as the Digimon enters play?
Yes, it does.
Q5: If I use this card's effect to play a Digimon card with an On Play effect, when does that effect activate?
It activates immediately after the card enters play. Even if there are other When Attacking and "when one of your Digimon attacks" effects waiting to be activated, the On Play effect was just triggered, so it activates first.
Q6: I use this card's effect to play a Digimon card. Can it attack this turn?
No, it's considered to have just entered play, so it can't attack.
Q7: If this Digimon has a level 4 or lower Digimon card in its digivolution cards, do I have to activate this card's effect?
Yes, as long as you are able to.
Data Sources
Lv.6 MetalGarurumon BT1-044 SR Mega | Data | Cyborg [When Attacking] Play 1 level 4 or lower digivolution card under this card as another Digimon without paying its memory cost.
Lv.6 MetalGarurumon BT1-044 SR Mega | Data | Cyborg [When Attacking] Play 1 level 4 or lower digivolution card under this card as another Digimon, without paying its memory cost.
Lv.6 MetalGarurumon BT1-044 SR Mega | Data | Cyborg [When Attacking] Play 1 level 4 or lower digivolution card under this card as another Digimon without paying its memory cost.
Lv.6 メタルガルルモン BT1-044 SR 究極体 | データ種 | サイボーグ型 【アタック時】このデジモンの進化元のLv.4以下のデジモンカード1枚を、コストを支払わずに別のデジモンとして登場させる。