Which one of the following classes of compounds is obtained by the cyclic polymerization of acetylene?

What is formed when acetylene reacts with alkaline $KMnO_4$?

Assertion : Acetylene on treatment with alkaline $KMnO_4$ produces acetaldehyde.
Reason : Alkaline $KMnO_4$ is a reducing agent.

In which of the following cases is the bond length between carbon and nitrogen minimum?

Which of the following is Lindlar catalyst?

$But-2-yne$ and hydrogen (one mole each) are separately treated with $(i)$ $Pd / C$ and $(ii)$ $Na / \text{liq. } NH_3$ to give the products $X$ and $Y$ respectively. Identify the incorrect statements.
$A$. $X$ and $Y$ are stereoisomers.
$B$. Dipole moment of $X$ is zero.
$C$. Boiling point of $X$ is higher than $Y$.
$D$. $X$ and $Y$ react with $O_3 / Zn + H_2O$ to give different products.
Choose the correct answer from the options given below: