The compound $A$ (major product) is

In the dehydrohalogenation of $2$-bromobutane,which conformation leads to the formation of $cis$-but-$2$-ene?

$CH_3-CH_2-CH(Br)-CH_3 \xrightarrow{Alc. KOH} X$ (major)
$CH_3-CH_2-CH(NMe_3^+) - CH_3 \xrightarrow{EtONa, \Delta} Y$ (major)
Product $(X)$ and $(Y)$ respectively are:

Which of the following compounds will undergo $E_2$ elimination reaction to give a single product in the presence of a strong base?

The major product of the following reaction is:

What is the correct order of $C-X$ bond strength in $CH_{3}X$?