If "Infernal Dragon" attacks, and is then flipped face-down, it will not be destroyed during the End Phase. Even if it is flipped face-up again during the same turn, it will not be destroyed.

If "Infernal Dragon" attacks, and control of it is switched to the opponent that turn, it will still be destroyed during the End Phase.

Even if "Infernal Dragon's" attack is negated by "Magic Cylinder", etc., it will still be destroyed during the End Phase.

The second effect of "Infernal Dragon" activates in the Graveyard. If it is destroyed while your opponent controls it, the original owner can choose to activate this effect.

The second effect of "Infernal Dragon" can be activated even if it was treated as an Equip Card when destroyed.

Infernal Dragon's" effect can be activated when it is destroyed by battle and sent to the Graveyard.: Infernal Dragon, Reverse of Neos: Infernal Dragon and Defender of the Forest, Green Baboon

Light and Darkness Dragon: If a monster with an optional Trigger Effect, like “Peten the Dark Clown” or “Infernal Dragon”, is destroyed by “Light and Darkness Dragon's” third effect, the timing to activate the effect of the destroyed monster is missed because immediately afterwards a monster is Special Summoned. The last thing to happen when resolving the effect is the Special Summon of a monster and not the destruction of “Peten the Dark Clown” or “Infernal Dragon”.The latest errata of "Light and Darkness Dragon" states that the Special Summon and destroying the cards occur simultaneously. Therefore, the effect of "Infernal Dragon" will not miss the timing.