The idiom "go bananas" means "Act crazily".
It is an informal expression used to describe someone becoming extremely excited or behaving in a wild, uncontrolled manner.
Coerced means forced or pressured to do something against one’s will.
Sentence: "He was coerced to give this confessional statement." makes logical and grammatical sense.
The preposition “Since” denotes point of time also reason.
He has been working here since 2015.
The preposition “For” denotes period of time.