Explanation:

- Sanjay Dutt vs. State of Maharashtra: This case related to the 1993 Mumbai blasts centered on TADA charges and the possession of illegal firearms but also involved discussions on confessional statements' retraction.

- Mohd. Amin vs. CBI: Primarily examined a crime involving forgery and cheating, with focus on the statements given and their eventual retraction.

- Both (a) and (b): As indicated above, both cases delve into the topic of confession retraction.

- Manjit Singh vs. CBI: This case was about a corruption case involving a bureaucrat, with less focus on confession retraction delay.

Correct Answer: Option: 3 - Both (a) and (b)