If you Special Summon "Apprentice Magician" face-down (such as with "Apprentice Magician’s” effect) then you do not place a Spell Counter.
An active "Skill Drain" can negate the effects of the "D.D. Warrior Lady," "D.D. Assailant," and "Apprentice Magician." But "The End of Anubis" has no effect on them, because they are on the field when their effects activate AND they do not target any card(s) in the Graveyard.
If a stolen Apprentice Magician is sent to the Graveyard by battle, the current controller of the card gets to search his deck for its effect.
You must show your opponent the monster you Special Summon.
For effects that place a Spell Counter, you can chain to the activation of those effects. The Spell Counter is actually placed when the effect resolves.