Bandai source: https://digimoncard.com/rule/pdf/qa_rule.pdf?v211029
Reason of updating: to clarify new effects/mechanics for ST9/10 and coming BT8 New Hero.
Main Phase
Q37: Are effects that last for a turn, such as [your turn] or [during this turn], no longer effective by the time you process the effect [at the end of the turn]?
A: No, the effect that lasts for the turn will continue to be effective until the turn change, so while processing the effect that will be exerted at the end of the turn, it is still before the turn change, so the effect remains.
Q38: What happens if the memory becomes 1 or more of the opponent and the turn ends, and the memory returns to 0 or more due to the effect exerted at "the end of the turn"?
A: If the memory returns to 0 or higher after performing all the effects that are exerted and applied at the end of the turn, the turn will not end and will continue.
Q39: When the memory becomes 1 or more of the opponent and the turn ends, if the memory returns to 0 or more due to the effect exerted at the end of the turn and the turn continues, it is already exerted [your turn], or what happens to effects that last for a turn, such as "during this turn"?
A: The effect that lasts for the duration of the turn will continue to be effective until the time when the turn is changed, so it will remain effective if the turn continues. The effect does not expire on the way.
Q40: The effect exerted at the end of the turn returns the memory to 0 or higher, and the turn will continue. After that, if the memory becomes 1 or more of the opponent again, will we trigger the effect that will be exerted at the end of the turn again?
A: Yes, you can.
Q41: I paid the play-cost to make a Digimon card with the effect of [On Play] appear, and as a result, the memory became 1 or more of the opponent. Will the effect exerted at the end of the turn and the [On Play] effect of this Digimon be triggered at the same time?
A: No, it will not be triggered at the same time, and the [On Play] effect will be exhibited first. Even if the memory becomes 1 or more of the other party due to payment of the play-cost etc., it will not be at the end of the turn immediately. After all the effects it exerts and triggers, if he has more than one of his opponent's memory, it's at the end of the turn.
Q42: Is it possible to deliberately put out a Digimon card in a hand that does not have a Digimon that meets the evolution conditions so that evolution fails and discard it?
A: No, you can not. Cards that cannot evolve cannot be presented from your hand.
Q43: Is it possible to cancel / cancel the evolution in the middle after taking out the evolution destination card from the hand?
A: No, you can not. If you show the card to evolve from your hand, you cannot stop the evolution in the middle.
Piercing
Q8: If my Digimon with multiple "Piecing" attacks the opponent's Digimon in battle, can I check multiple times without having "Security Attack +"?
A: No, you can not. Even if you have multiple " Piercing", the number of checks will not increase.
De-digivolve
Q7: Is it possible to have an opponent's Lv.3 Digimon who has a Lv.3 or higher Digimon card as an evolution source discard the card with "De-digivolve" by some effect?
A: No, even if a Lv.3 Digimon has a Lv.3 or higher Digimon card as its evolution source, it cannot be destroyed (remove) by "De-digivolve" for that Digimon.