The number of possible isomers for butene $(C_4H_8)$ is..........

Which of the following optically active compounds has the maximum number of chiral carbons?

According to $CIP$ sequence rule,the correct arrangement in order of decreasing priority is :-

Consider the sets $I$,$II$,and $III$. Identify the set$(s)$ which is (are) correctly matched.
$I$. $\text{Staggered ethane} > \text{eclipsed ethane} \dots \dots \dots \text{torsional strain}$.
$II$. $2, 2-\text{Dimethylbutane} > 2-\text{methylpentane} \dots \dots \dots \text{boiling point}$.
$III$. $cis-\text{but}-2-\text{ene} > trans-\text{but}-2-\text{ene} \dots \dots \dots \text{dipole moment}$.

$A$ naturally occurring substance has the constitution shown below. How many stereoisomers may have this constitution?

Which of the following compounds does not exhibit keto-enol tautomerism?