How many structural isomers are possible for a compound with molecular formula $C_3H_7Cl$?

Tautomerism is not exhibited by

How many structural isomers are possible for $C_3H_6ClBr$ and how many of them are optically active?

Which of the following compounds will exhibit metamerism?

Compounds $P$ and $R$ in the following reaction are:

For which of the following parameters would the structural isomers $C_2H_5OH$ and $CH_3OCH_3$ be expected to have the same values? (Assume ideal behavior)