Array scoresList has $10$ elements with indices $0$ to $9,$ accessed as scoresList$[0]$ to scoresList$[9].$

$1)$

Assign the first element in scoresList with $77.$

$2)$

Assign the second element in scoresList with $77.$

$3)$

Assign the last element with $77.$

$4)$

If that array instead has $100$ elements, what is the last element's index?

$5)$

If the array's last index was $499,$ how many elements does the array have?