REDU format ruling
Different Dimension Dragon

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)This card cannot be destroyed by Spell/Trap effects that do not target it. This card cannot be destroyed by battle with a monster that has 1900 or less ATK.
Rulings
- Different Dimension Dragon cannot be destroyed by Fissure, Mirror Force, etc. Also, if Different Dimension Dragon is your only monster on your side of the field, your opponent cannot activate effects like Fissure, Mirror Force, Raigeki, etc.
- Different Dimension Dragon can be destroyed while in your hand or Deck with Chain Destruction.
- If Different Dimension Dragon is face-down, it can be destroyed by Raigeki and similar non-targeting cards.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.