In $Group-13$ $(IIIA)$,$Tl$ (thallium) shows $+1$ oxidation state while other members show $+3$ oxidation state. Why?

Which of the following reaction products are represented correctly?
$(a)\ P_4 + 3NaOH(dil) + 3H_2O \to PH_3 + 3NaH_2PO_2$
$(b)\ 3Br_2 + 6NaOH(conc) \to 5NaBr + NaBrO_3 + 3H_2O$
$(c)\ NCl_3 + 3H_2O \to NH_3 + 3HOCl$
$(d)\ I_2 + 2NaOH \to NaI + NaOI + H_2O$
$(e)\ Al_4C_3 + 12H_2O \to 4Al(OH)_3 + 3CH_4$
$(f)\ N_2O_4 + H_2O \to HNO_3 + HNO_2$
$(g)\ NH_4NO_3 + NaOH \to NH_3 + NaNO_3 + H_2O$
Correct options are:

In the following reaction,identify the nature of the products formed by the complete hydrolysis of $\underline{P}_4O_8$ at $R.T$:
$\underline{P}_4O_8 + H_2O \longrightarrow H_3PO_3 + H_3PO_4$

Heating $(NH_4)_2Cr_2O_7$ releases a gas. Which of the following also produces the same gas?

What is the nature of hydrides and oxides of Group $15$ elements?

The number of non-ionisable hydrogen atoms present in the final product obtained from the complete hydrolysis of $PCl_{5}$ is :