The following compounds are identical with respect to:

$P$ 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 $2$.

The structure of $E-(S)-1$-chloro-$1$-bromo-$2$-methyl-$2$-hexene is best represented by

How many stereoisomers are possible for the following molecule?

$A$ compound with the molecular formula $C_4H_{10}O$ exhibits which type of isomerism?

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