Arrange the given amines in decreasing order of their basicity.

Order of basic strength: $(A) Ph-NH_2$,$(B) Ph-NH-CH_3$,$(C) Ph-N(CH_3)_2$,$(D) \text{o-toluidine (2-methylaniline)}$

Which of the following amines undergoes acylation reaction?

Aniline reacts with mixed acid (conc. $HNO_3$ and conc. $H_2SO_4$) at $288 \ K$ to give $P$ $(51 \%)$,$Q$ $(47 \%)$ and $R$ $(2 \%)$. The major product$(s)$ of the following reaction sequence is (are):
$R$ $\xrightarrow[2) Br_2, CH_3CO_2H]{1) Ac_2O, \text{pyridine}}$ $\xrightarrow{3) H_3O^+}$ $\xrightarrow{4) NaNO_2, HCl / 273-278 \ K}$ $\xrightarrow{5) EtOH, \Delta}$ $\xrightarrow{6) Sn/HCl}$ $\xrightarrow{7) Br_2/H_2O \text{ (excess)}} \text{Major Product}$

Which of the following is most basic?

Arrange the following in decreasing order of their basic strength:
$C_6H_5NH_2, C_2H_5NH_2, (C_2H_5)_2NH, NH_3$