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

In the arrangement $P, 2, 6, M, 9, K, S, 4, V, 7$,the positions of the $1^{st}$ and the $6^{th}$ elements are interchanged,those of the $2^{nd}$ and the $7^{th}$ are interchanged,and so on. Then,which of the following will be the $4^{th}$ element from the left end in the new arrangement?

Fill in the blank space for the given series with the correct alternative.
$4, 32, 128, (\ldots)$

Find out the missing letters for the given series from the given alternatives.
$a....abbb...ccccd.....ddccc.....bb....ba$

Fill in the blank space for the given series with the correct alternative.
$90, 180, 12, 50, 100, 200, (\ldots), 3, 50, 4, 25, 2, 6, 30, 3$

Fill in the blank space for the given series with the correct alternative.
$123456147, 12345614, 2345614, 234561, (...)$