Isomers have the same ...........

Determine the configuration at $C-2$ and $C-3$ of the given compound.

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

The correct relationship between molecules $I$ and $II$ is:

How many total representations of lactic acid are possible in Fischer projection for both $(d)$ and $(l)$ isomers?

Which of the following is the least stable conformer of cyclohexane?