What should come next in the following letter series?
$bac, bacd, bacde, bacdef, bacd?$

Study carefully the following arrangement of letters, digits and symbols to answer these

questions.

$M, 7 ,\&, 8, L ,P ,@ ,Q ,N ,\beta ,T ,Y ,3 ,2 ,= ,E ,\$ ,4 ,9 ,\#, G ,H ,5$

$'78'$ is to $'P?6'$ and $'?N'$ is to $'T32'$ in the same way as $2 E'$ is to $\ldots \ldots \ldots . . .$ in the arrangement.

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

Find out the wrong term from the given series: $8, 27, 125, 343, 1331$.

Fill in the blank space for the given series with the correct alternative.
$3, 4, 7, 7, 13, 13, 21, 22, 31, 44, (\ldots)$

Fill in the blank space for the given series with the correct alternative.
$1, 6, 13, 22, 33, (...)$