Which of the following substances is ionic?

When phosphine is passed through an aqueous solution of copper sulphate,the product produced is:

Which of the following gases is inert at room temperature?

In the following reaction,identify the nature of the product formed by the underlined atom upon complete hydrolysis at $R.T$.:
$H_4\underline{P}_2O_8 + H_2O \longrightarrow H_3PO_4 + H_2O_2$

The correct code for stability of oxidation states for given cations is:
$(i)$ $Pb^{2+} > Pb^{4+}, Tl^{+} < Tl^{3+}$
$(ii)$ $Bi^{3+} < Sb^{3+}, Sn^{2+} < Sn^{4+}$
$(iii)$ $Pb^{2+} > Pb^{4+}, Bi^{3+} > Bi^{5+}$
$(iv)$ $Tl^{3+} < In^{3+}, Sn^{2+} > Sn^{4+}$
$(v)$ $Sn^{2+} < Pb^{2+}, Sn^{4+} > Pb^{4+}$
$(vi)$ $Sn^{2+} < Pb^{2+}, Sn^{4+} < Pb^{4+}$

$N_2$ forms $NCl_3$,whereas $P$ can form both $PCl_3$ and $PCl_5$. Why?