The reagents required for the following two-step transformation are:

The major product of the following reaction is:
(Structure of $4-$bromo-pent$-2-$en$-2-$amine derivative) $\xrightarrow[{S_N2}]{{KOH}}$

Formation of $2-$butene from $2-$bromobutane is according to

The given compound $CH_3-O-CH_2-Br$ undergoes which of the following reactions?

The reaction $RCl + NaI \xrightarrow{\text{Acetone}} R-I + NaCl$ is known as:

The mechanism of $S_{N}1$ reaction is given as:
$R-X$ $\rightarrow R^{\oplus} X^{\ominus}$ $\rightarrow R^{\oplus} | X^{\ominus}$ $\xrightarrow{Y^{\ominus}} R-Y + X^{\ominus}$
(Ion pair) (Solvent separated ion pair)
$A$ student writes general characteristics based on the given mechanism as:
$(a)$ The reaction is favoured by weak nucleophiles
$(b)$ $R^{\oplus}$ would be easily formed if the substituents are bulky
$(c)$ The reaction is accompanied by racemization
$(d)$ The reaction is favoured by non-polar solvents.
Which observations are correct?