A: In aniline the lone pair on nitrogen is delocalised into the ring, lowering basicity. Benzylamine's nitrogen lone pair is not delocalised, so benzylamine is more basic than aniline. Statement A is correct.

B: Gabriel synthesis works only with reactive alkyl halides (S${}_{\text{N}}$2); aryl halides do not react with the phthalimide ion. So $p$-anisidine cannot be made by this method. Statement B is incorrect.

C: Hofmann bromamide degradation of an amide ${\text{R-CONH}}_2\to {\text{R-NH}}_2$ shortens the chain by one carbon. From ${\text{PhCH}}_2{\text{CONH}}_2$ this gives ${\text{PhCH}}_2{\text{NH}}_2$, which is an aliphatic (benzylic) primary amine, not an aromatic amine. Statement C is incorrect.

D: 4-Nitroaniline diazotised at 0${}^{\circ }$C and warmed gives 4-nitrophenol, which is acidic enough to dissolve in NaOH. Statement D is correct.

Incorrect statements: B and C.