Question

Why is $AgN{O}_3$ not used in electroplating? Are there more such cases where a compound is a unit for use in electroplating?

Answer 1

The migration of Ag+ in silver nitrate solution is very fast leading to an uneven deposition of the metal silver on the substrate. Hence, it is not used for electroplating.
There are no specific examples of compounds unfit for electroplating. It depends on the environment and the additional substances present in the electrolyte and hence, is highly subjective.