Crossword puzzle clue "sought answers"

Sought answers

How many letters are in the longest answers in this puzzle - or how many of these answers there are

Letter appearing only in down answers; its opposite appears only in across answers

Order sought by an accused before trial

Pope who sought Charlemagne's aid

Where Stanley sought Livingstone

He sought "the monstrousest parmacetty" [3-10]

Sought the bull's-eye