Find out the missing number in the following sequence:
$1, 3, 3, 6, 7, 9, ?, 12, 21$

These questions are based on the following letter/number/symbol arrangement. Study it carefully and answer the questions that follow.

$5, D,H,E, \star, 7,9, \$ ,F,I ,6 ,R ,\% ,L ,1 ,A,J, 3, B, \# ,4 ,@ ,K,P ,8, U,M ,2$

If all the symbols are removed from the above arrangement, which element will be third to the left of thirteenth from the left?

How many such digits are there in the number $5831649$ each of which is as far away from the beginning of the number as when the digits are rearranged in ascending order?

Find out the missing term for the given series from the given alternatives.
$P 3 C, R 5 F, T 8 I, V 12 L, ?$

Choose the correct alternative to complete the series: $m, n, o, p, q, o, p, q, r, s, \dots$

Choose the correct alternative to fill in the blanks in the series: $ba....b...aabb....a........a...bb$