REDU format ruling
Spear Cretin

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)FLIP: When this card is sent to the Graveyard after being flipped, each player selects 1 monster from their Graveyard, and Special Summons it in face-up Attack Position or face-down Defense Position.
Rulings
- If you can Special Summon a monster but your opponent cannot, you will still Special Summon. If your opponent can Special Summon a monster and you cannot, your opponent will still Special Summon.
- Special Summoning a monster is optional.
- Spear Cretin cannot Special Summon itself from the GY, but it can Special Summon another copy of Spear Cretin.
- After Spear Cretin is flipped face-up, if it and another monster you control are destroyed by the same effect, you can Special Summon the other destroyed monster.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.