When using this card's {Security} [End of Your Turn] effect to play BT25-059 [Ceresmon], if I activate BT25-059 [Ceresmon]'s 1st effect, is the play cost reduced by a total of 12?

If I activate this card's [All Turns] effect when multiples of my other specified Digimon or Tamers would leave the battle area at the same time by one of my effects, are all of those Digimon or Tamers prevented from leaving?

I activated this card's [All Turns] effect when multiples of my Digimon would leave the battle area by an opponent's effect, and I deleted this card. Can I then activate this card's [On Deletion] effect before all of my opponent's effects are resolved?