An alkyl halide $C_3H_7Cl$,on reaction with a reagent $X$ gave the major product $Y$ $(C_4H_7N)$. $Y$ on hydrolysis released a gas,which turns red litmus to blue. What are $X$ and $Y$?

The reaction of an alkyl halide with $Mg$ in dry ether produces ..... as the product.

Arrange the following three chlorides in decreasing order of their reactivity towards $S_{N^1}$ reaction.

The reaction of $1$-chlorobutane with alcoholic potash gives $......$.

The major product obtained in the following reaction is $:$

Consider the $S_N1$ solvolysis of the following halides in aqueous formic acid:
$(I)$ $CH_3-CH(CH_3)-CH(Br)-CH_3$
$(II)$ $CH_3-C(CH_3)(Br)-CH_3$
$(III)$ $C_6H_5-CH(Br)-C_6H_5$
$(IV)$ $C_6H_5-CH(Br)-CH_3$
Which one of the following is the correct sequence of the halides given above in the decreasing order of their reactivity?