QIf I put Spartoi Sergeant onto my field with this follower's Fanfare ability, can I play Spartoi Sergeant's Fanfare ability before giving it +1/+1?

ANo. You finish resolving this follower's Fanfare ability before playing Spartoi Sergeant's Fanfare ability.

QWhen playing this follower's Fanfare ability, do I give +1/+1 (or +3/+3) to each follower on my field other than this follower, or each follower other than the Abysscraft followers I just put from my cemetery onto my field?

AYou give the buff to each follower on your field other than this follower.

QIf I have exactly 10 cards in my cemetery when I play this follower's Fanfare ability, does Necrocharge (10) still trigger? If I have exactly 20, does Necrocharge (20) still trigger?

AYes, and yes. Necrocharge references the number of cards in your cemetery at the moment the effect with Necrocharge begins to be resolved.

QIf I steal an enemy Abysscraft follower when this follower is on my field, does this follower's ability give the stolen follower Rush?

AYes, it does.

QDoes this follower give itself Rush?

AYes, it does.