What is the number of $\sigma$ and $\pi$ bonds in tetracyanoethylene?

Match the List-$I$ with List-$II$:

List-$I$ (Classification of molecules based on octet rule)	List-$II$ (Example)
$A$. Molecules obeying octet rule	$I$. $NO, NO_2$
$B$. Molecules with incomplete octet	$II$. $BCl_3, AlCl_3$
$C$. Molecules with odd electron	$III$. $H_2SO_4, PCl_5$
$D$. Molecules with expanded octet	$IV$. $CCl_4, CO_2$

Choose the correct answer from the options given below:

Compare the $x$ and $y$ bond lengths in the following molecules:
Structure $1$: $HO-S(=O)-S(=O)-OH$ (where $x$ is the $S-S$ bond length)
Structure $2$: $HO-S(=O)_2-S(=O)-OH$ (where $y$ is the $S-S$ bond length)

Which of the following odd electron species is planar?

Bond length of ethane $(I)$, ethene $(II)$, acetylene $(III)$ and benzene $(IV)$ follows the order

Which of the following sequences does not contain an isoelectronic species?