Which of the following cations will give a precipitate with $Na_2C_2O_4$ solution in the presence of acetic acid?

Which of these reactions is correct?

The reagent used for the identification of $Ni^{2+}$ ions is .....

$(T)$ imparts violet colour $\xrightarrow{compd.\,(U) + conc.\,H_2SO_4}$ $(V)$ Red gas $\xrightarrow{NaOH + AgNO_3}$ $(W)$ Red ppt. $\xrightarrow{NH_3\,soln.}$ $(X)$
$(W)$ Red ppt. $\xrightarrow{dil.\,HCl}$ $(Y)$ white ppt.
$(U)$ $\xrightarrow[\Delta]{NaOH}$ $(Z)$ gas (gives white fumes with $HCl$)?
$(T)$ sublimes on heating
Identify $(T)$ to $(Z).$

Given below are certain cations. Using inorganic qualitative analysis,arrange them in increasing group number from $0$ to $VI$.
$A$. $Al^{3+}$ $B$. $Cu^{2+}$ $C$. $Ba^{2+}$ $D$. $Co^{2+}$ $E$. $Mg^{2+}$
Choose the correct answer from the options given below.

Statement-$1$: Few drops of $HNO_3$ are added before proceeding to $III^{rd}$ group.
Statement-$2$: For the oxidation of $Fe^{+2} \rightarrow Fe^{+3}$.