You cannot use substitute Fusion Material Monsters such as "Beastking of the Swamps" to Fusion Summon this card. You can use the effects of "Metamorphosis", "Magical Scientist", and "Summoner of Illusions" to Special Summon this card.
If your opponent Flip Summons a monster with a Flip Effect, and chains a card like "Offerings to the Doomed" to destroy "Fiend Skull Dragon", the Flip Effect will not be negated since "Fiend Skull Dragon" is no longer on the field when the Flip Effect resolves, and it will only negate Flip Effect "as long as this card remains face-up on the field".
The opponent may activate a Trap Card that targets "Fiend Skull Dragon", but its effect will be negated and the Trap Card destroyed.
Cards such as "Torrential Tribute", "Bottomless Trap Hole", "Mirror Force", and "Last Turn" will all apply their effects to "Fiend Skull Dragon" because these cards do not target.
You can activate "Call of the Haunted" to Special Summon "Fiend Skull Dragon". After it resolves, "Call of the Haunted" will be destroyed and "Fiend Skull Dragon" will remain on the field. Remember that "Fiend Skull Dragon" must have been properly Fusion Summoned previously in order to Special Summon it from the Graveyard.
You can chain "Call of the Haunted" to the activation of a Flip Effect to Special Summon "Fiend Skull Dragon", and the Flip Effect will be negated.