The positions of how many digits in the number $7,3,5,4,6,1,2$ will remain unchanged after the digits within the number are rearranged in descending order from left to right?

Fill in the blank space for the given series with the correct alternative.
$1, 3, 4, 8, 15, 27, (\ldots)$

Study the following arrangement carefully and answer the questions given below:

$7, R,E,T ,4 ,A ,9 ,\% ,D,F, 1, U, \# ,B ,@ ,8 ,H,I ,$©$, W,M, \star, 3,2 ,V ,\$ ,5 ,N,P,6, Q$

How many such vowels are there in the above arrangement, each of which is immediately followed by a symbol?

Fill in the blank space for the given series with the correct alternative.
$563, 647, 479, 815, (...)$

Study the following arrangement carefully and answer the questions given below:
$R, 4, E, J, 5, T, 1, A, M, Q, 3, 8, N, I, K, 7, W, F, 6, D, 9, U, 2, Y, V$
Four of the following five are alike in a certain way based on their positions in the above arrangement and so form a group. Which is the one that does not belong to this group?

Find out the missing letters for the given series from the given alternatives:
$abca . . . . . bcaab . . . . . ca . . . . . bbc . . . . . a$