Identify the product ' $A$ ' obtained in following reaction.

N -alkyl phthalimide $\xrightarrow{\mathrm{N}_2 \mathrm{OH}_{(a q)}}$ sodium phthalate + A

Which among the following is the conjugate base of $\mathrm{HClO}_4$ ?

Which from following polymers contain - CO - NH - linkage in it?

Identify the product of ozonolysis of but-2-ene from following: