Rulings
Q1: Does this card's inherited effect activate when I attack my opponent's Digimon?
No. If your opponent doesn't block, the effect doesn't activate. Regardless of what the target of attack is, the effect activates when a Digimon with this card in its digivolution cards attacks an opponent's Digimon and has its attack target changed to an opponent's Digimon that blocks.
Data Sources
EN
Official English Card Listworld.digimoncard.com
Lv.5 MetalGreymon ST1-09 R Ultimate | Vaccine | Cyborg - --- Inherited: [Your Turn] When this Digimon is blocked, gain 3 memory.
A
Official English (Asia) Card Listen.digimoncard.com
Lv.5 MetalGreymon ST1-09 R Ultimate | Vaccine | Cyborg - --- Inherited: [Your Turn] When this Digimon is blocked, gain 3 memory.
W
DCG Wikidigimoncardgame.fandom.com
Lv.5 MetalGreymon ST1-09 R Ultimate | Vaccine | Cyborg --- Inherited: [Your Turn] When this Digimon is blocked, gain 3 memory.
JP
Official Japanese Card Listdigimoncard.com
Lv.5 メタルグレイモン ST1-09 R 完全体 | ワクチン種 | サイボーグ型 --- Inherited: 【自分のターン】このデジモンがブロックされたとき、メモリーを+3する。