The two compounds given below are:

Which of the following methods of structural formula representation conventionally uses a point for the front carbon and a circle around it for the rear carbon?

The starting material is propene $(CH_3-CH=CH_2)$. The reaction with $H_3O^+$ (acid-catalyzed hydration) follows Markovnikov's rule to give $A$ (propan$-2-$ol,$CH_3-CH(OH)-CH_3$). The reaction with $(i) BH_3/THF$ followed by $(ii) H_2O_2/OH^-$ (hydroboration-oxidation) follows anti-Markovnikov's rule to give $B$ (propan$-1-$ol,$CH_3-CH_2-CH_2OH$). What is the relationship between products $A$ and $B$?

The type of isomerism shown by the following compounds is:
$CH_3-(CH_2)_3-O-CH_3$
$CH_3-CH_2-O-CH_2-CH_2-CH_3$
$CH_3-CH(CH_3)-O-CH_2-CH_3$

The pair of metamers is :-

Which of the following pairs of molecules are metamers?