Glass reacts with $HF$ to produce

Rationalise the given statements and give chemical reactions:
$1$. Lead $(II)$ chloride reacts with $Cl_2$ to give $PbCl_4$.
$2$. Lead $(IV)$ chloride is highly unstable towards heat.
$3$. Lead is known not to form an iodide,$PbI_4$.

An inorganic compound $(A)$ made of the two most occurring elements in the earth's crust,having a polymeric tetrahedral network structure. With carbon,compound $(A)$ produces a poisonous gas $(B)$ which is the most stable diatomic molecule. Compounds $(A)$ and $(B)$ are:

Assertion $(A)$: Silicones are used for water proofing of fabrics.
Reason $(R)$: The repeating unit in silicones is $R_2SiO$.

Which of the following compounds is $NOT$ acidic in nature?

What is meant by $Tin \ Plague$?