Let's say I have Caius or Raiza in hand. Then I tribute summoned Caius/Raiza but set it face down.
Q1- If next turn I flip it face up in Attack position, does it's effect activate?
Q2- If opponent attacks my set face-down Caius/Raiza, does it's effect activate?
Q3- What if I tribute summoned Caius/Raiza (its effect activated normally), then used Book of Moon to flip it face down, then flipped it face up in Attack position again, does its effect activate again?