$AgNO_3$ does not give a precipitate with $CHCl_3$ because

Assertion $(A)$: $1-$Bromopentane reacts with $AgCN$ to give pentylisocyanide.
Reason $(R)$: $AgCN$ is mainly ionic in nature.

Among the following,the compound which undergoes the fastest solvolysis is

Which of the following undergoes nucleophilic substitution by $S_N1$ mechanism?

Ethanolic $KOH$ gives

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?