Knightmon

Q:Do I have to choose an opponent's Digimon for this card's [End of Opponent’s Turn] effect?

A:No, you don't have to choose an opponent's Digimon.

Q:If I choose an opponent's Digimon that can't attack for this card's [End of Opponent’s Turn] effect, does my opponent attack with that Digimon?

A:No, they can't attack using a Digimon that can't attack.

Q:An opponent's Digimon is attacking using an effect at the end of their turn. If I choose an opponent's Digimon for this card's [End of Opponent’s Turn] effect, does my opponent attack with that Digimon?

A:No, your opponent can't attack using that Digimon. A new attack declaration can't be made during an attack. In such cases, even if you choose an opponent's Digimon for this card's [End of Opponent’s Turn] effect when there is already an attacking Digimon, your opponent can't attack with the chosen Digimon.

Q:Can I choose a Digimon that isn't affected by effects for this card's [End of Opponent’s Turn] effect and have it attack?

A:Yes, you can choose a Digimon that isn't affected by effects for this and have it attack. Such Digimon aren't affected by effects, but they can be chosen. In addition, "your opponent attacks with the chosen Digimon" in this card's [End of Opponent’s Turn] effect affects a player, therefore your opponent must attack with the chosen Digimon if it can attack.