Which of the following compounds is insoluble even in hot concentrated $H_2SO_4$?

Which one gives only one monosubstitution product on chlorination?

When a certain alkane is mixed with chlorine and irradiated with ultraviolet light,only one monochloroalkane is formed. This alkane is likely to be:

$Ph^{-}MgCl \xrightarrow{\text{Hydrolysis}} \text{Product}$
Product will be

$A$ hydrocarbon $A$ $(V.D. = 36)$ forms only one monochloro substitution product. $A$ will be:

Give reason: Why is the fluorination of alkanes not easy to control?