QAn opponent only has a Mordecai the Duelist on their field, and I summon and destroy an Underworld Watchman Khawy and Yuzuki, Righteous Demon with this follower's Fanfare ability. If I choose to destroy that enemy Mordecai the Duelist with Underworld Watchman Khawy's Last Words ability first, does my Yuzuki, Righteous Demon's Fanfare ability cause that opponent to bury the Mordecai the Duelist summoned by its own Last Words?

ANo. The active player always resolves their abilities before non-active players.

In this case, after resolving Underworld Watchman Khawy's Last Words ability, the opponent's Mordecai the Duelist is destroyed and its Last Words ability triggers and becomes pending. Then, as the active player, you must resolve Yuzuki, Righteous Demon's Fanfare ability first. At this point the Mordecai the Duelist is in the opponent's cemetery, so nothing happens because your opponent doesn't have any followers on the field they can bury. Afterwards, the opponent resolves their Mordecai the Duelist's Last Words ability.

QIf I summon and destroy Apostle of Lust and 3 other Demon followers with this follower's Fanfare ability, do I give my leader 3 defense?

AYes, you do.

QIf I summon and destroy a Howling Demon and Mordecai the Duelist with this follower's Fanfare ability, and I choose to give my leader -3 defense with Mordecai the Duelist's Last Words ability first, can I select an enemy follower on the field and deal it 8 damage?

AYes. If you choose to resolve Mordecai the Duelist's Last Words first, Sanguine becomes active for you because your leader has lost defense during your turn.

QI have 6 cards in my cemetery. If I summon and destroy 4 followers, including a Rulenye, Omen of Silence with this follower's Fanfare ability, do I still select an enemy follower that costs 3 play points or less on the field and destroy it?

AYes. After resolving this follower's Fanfare ability, the number of cards in your cemetery will be 10 when you resolve Rulenye, Omen of Silence's Fanfare ability, so you would meet the requirements for "Necrocharge (10)."

QWhen playing this follower's Fanfare ability, if multiple followers with Fanfare and/or Last Words abilities are summoned and destroyed, in what order should I resolve them?

ASince the Fanfare and Last Words abilities are triggered simultaneously, you may resolve the pending abilities in any order after you resolve this follower's Fanfare ability.