Which of the following statements is not correct?

Among the following oxides of $p$-block elements,the number of oxides having amphoteric nature is: $Cl_2O_7, CO, PbO_2, N_2O, NO, Al_2O_3, SiO_2, N_2O_5, SnO_2$

Thermodynamically,the most stable form of carbon is

Explain the following reactions:
$(a)$ Silicon is heated with methyl chloride at high temperature in the presence of copper.
$(b)$ Silicon dioxide is treated with hydrogen fluoride.
$(c)$ $CO$ is heated with $ZnO$.
$(d)$ Hydrated alumina is treated with aqueous $NaOH$ solution.

$RCl$ $\xrightarrow[Si]{Cu \text{ powder}} R_2SiCl_2$ $\xrightarrow{H_2O} R_2Si(OH)_2$ $\xrightarrow{\text{condensation}} A$
Compound $(A)$ is:

Phosphorus has the oxidation state of $+3$ in