Identify $(P)$ and $(Q)$ in the following reaction:
$2 CH_3 Cl + Si$ $\xrightarrow[570 \ K]{\text{Cu powder}} (P)$ $\xrightarrow{H_2 O} (Q)$ $\longrightarrow \text{Straight chain polymer}$

Evaluate the following statements related to group $14$ elements for their correctness.
$(A)$ Covalent radius decreases down the group from $C$ to $Pb$ in a regular manner.
$(B)$ Electronegativity decreases from $C$ to $Pb$ down the group gradually.
$(C)$ Maximum covalence of $C$ is $4$ whereas other elements can expand their covalence due to presence of $d$ orbitals.
$(D)$ Heavier elements do not form $p\pi-p\pi$ bonds.
$(E)$ Carbon can exhibit negative oxidation states.
Choose the correct answer from the options given below:

What are the ions called that possess properties similar to halide ions and consist of two or more electronegative atoms,at least one of which is nitrogen?

The composition of common glass is:

Which of the following hydrides is the least stable?

In the following reaction,identify the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T.$:
$H_2\underset{-}{S}_2O_7 + H_2O \longrightarrow 2H_2SO_4$