What is the value of $K_{s p}$ for saturated solution of $\mathrm{Ba}(\mathrm{OH})_2$ having pH 12 ?

Benzonitrile on reduction with stannous chloride in presence of hydrochloric acid followed by acid hydrolysis forms,

Identify from following salts so that the solubility of salt in water decreases with increase in temperature.

Which from following polymers is obtained by condensation polymerisation method?