Which among the following compounds is the most acidic?

Heating a mixture of ethyl alcohol and acetic acid in the presence of conc. $H_2SO_4$ produces a fruity-smelling compound. This reaction is called:

Considering the acidity of carboxylic acids:
$(I) PhCOOH$
$(II) o-NO_2C_6H_4COOH$
$(III) p-NO_2C_6H_4COOH$
$(IV) m-NO_2C_6H_4COOH$
What is the correct order of acidic strength?

Heating chloroform with aqueous sodium hydroxide solution forms:

Give the reactions of benzoic acid $(C_6H_5COOH)$ with the following:
$(i)$ Sodium metal
$(ii)$ Solution of sodium hydroxide $(NaOH)$
$(iii)$ Solution of sodium bicarbonate $(NaHCO_3)$
$(iv)$ $P_2O_5$ or conc. $H_2SO_4$ $+$ heat
$(v)$ $PCl_5$
$(vi)$ $PCl_3$
$(vii)$ $SOCl_2$
$(viii)$ $NH_3$ $+$ high temperature
$(ix)$ $LiAlH_4$ / ether or $B_2H_6$
$(x)$ Sodalime $(NaOH + CaO)$ $+$ heat
$(xi)$ Conc. $HNO_3$ $+$ conc. $H_2SO_4$ $+$ heat
$(xii)$ $Br_2 + FeBr_3$
$(xiii)$ Oleum $(H_2SO_4 + SO_3)$ $+$ heat

$G$ in the above sequence of reactions is