Which element of group $13$ does not show the group valency in its compounds?

Identify the correct statements about $p$-block elements and their compounds.
$(A)$ Non-metals have higher electronegativity than metals.
$(B)$ Non-metals have lower ionisation enthalpy than metals.
$(C)$ Compounds formed between highly reactive non-metals and highly reactive metals are generally ionic.
$(D)$ The non-metal oxides are generally basic in nature.
$(E)$ The metal oxides are generally acidic or neutral in nature.

The number of acidic protons present in $H_3PO_2$,$H_3PO_3$ and $H_3PO_4$ respectively,are .....

The correct orders among the following are
$A$. Atomic radius $: B < Al < Ga < In < Tl$
$B$. Electronegativity $: Al < Ga < In < Tl < B$
$C$. Density $: Tl < In < Ga < Al < B$
$D$. $1^{st}$ Ionisation Energy $: In < Al < Ga < Tl < B$
Choose the correct answer from the options given below $:$

Explain why the following compounds behave as Lewis acids?
$(A)$ $BCl_3$
$(B)$ $AlCl_3$

Relative stability orders of $+1$ and $+3$ oxidation states of $Ga, In, Tl$ are respectively: