The effects trigger simultaneously, so the player can choose the activation order. However, if you first activate <Ascension> and this card is removed from the trash, the other effects on this card that were pending activation can no longer activate.

The player that activated this card's effect. The cards to return and their order are chosen by the player that activated this effect, then they are returned to the deck.

Yes, it's met.

No, you can't. A "by" condition can't be met if only some of the required actions are performed. In order for the conditions for this card's [On Play] [When Digivolving] effect to be met, you must return 2 cards from your opponent's trash to the bottom of the deck.

No, you can't activate it. When a card with an effect that's pending activation leaves its current area while activation is pending, the effect can no longer be activated. In this case, the deleted card's [On Deletion] effect triggers, but it's removed from the trash before the effect can activate.

Its DP is reduced by 15000. You count the total number of colors on the returned cards.