Which of the following statements are correct about this reaction? (i) The given reaction follows the SN2 mechanism. (ii) (b) and (d) have the opposite configuration. (iii) (b) and (d) have the same configuration. (iv) The given reaction follows the SN1 mechanism.
Which of the following statements are correct about this reaction? (i) The given reaction follows the SN2 mechanism. (ii) (b) and (d) have the opposite configuration. (iii) (b) and (d) have the same configuration. (iv) The given reaction follows the SN1 mechanism.

Option (i) and (ii) are the answers.

Alkyl halide is the main reactant in the given reaction. A transient condition is found here, in which one bond is broken and another is created synchronously, that is, in one step. As a result, it follows the SN2 mechanism.
The nucleophile approaches the carbon at an angle of 180 degrees to the leaving group in this process. As a result, the reactant and product have a configuration that is diametrically opposed.