Crossword puzzle clue "certain 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

Instrument that hints at the missing parts of certain answers in this puzzle

Word that can precede each set of circled letters, forming a literal hint for entering certain answers in this puzzle

Title on certain language videos ... with a hint to entering six answers in this puzzle

Psalm 100 excerpt suggested by six puzzle answers and graphically represented by certain black squares in this puzzle

Traditional golf pants, and a hint to why certain puzzle answers are wrong

Affliction that, read a certain way, appears in this puzzle's three theme answers