Which of the following is a meso compound?

Which of the following pairs represent a pair of diastereomers?

The electrophile,$E^{\oplus}$ attacks the benzene ring to generate the intermediate $\sigma-$complex. Of the following,which $\sigma-$complex is of the lowest energy?

The correct statement$(s)$ about the compound given below is(are):
$A$. The compound is optically active
$B$. The compound possesses centre of symmetry
$C$. The compound possesses plane of symmetry
$D$. The compound possesses axis of symmetry

$P$ and $Q$ are isomers of dicarboxylic acid $C_4H_4O_4$. Both decolorize $Br_2/H_2O$. On heating,$P$ forms a cyclic anhydride.
Upon treatment with dilute alkaline $KMnO_4$,$P$ as well as $Q$ could produce one or more than one from $S$,$T$,and $U$.
$1.$ Compounds formed from $P$ and $Q$ are,respectively:
$(A)$ Optically active $S$ and optically active pair $(T, U)$
$(B)$ Optically inactive $S$ and optically inactive pair $(T, U)$
$(C)$ Optically active pair $(T, U)$ and optically active $S$
$(D)$ Optically inactive pair $(T, U)$ and optically inactive $S$
$2.$ In the following reaction sequences,$V$ and $W$ are respectively:
Give the answer for question $1$ and $2$.

Ethyl $3$-oxobutanoate and ethyl $3$-hydroxybut-$2$-enoate are ................... of each other.