Is Apostle Nick Cheung an undercover agent?

Nick Cheung in "Walker" is an undercover agent.

In the movie "Walker", Nick Cheung is the real undercover agent, but Louis Koo borrowed his identity and pretended to be a member of the police to contact the police.

Introduction to "Walker":

This film tells the story of senior police officer Kang Sir who was killed. Before his death, he destroyed all undercover information. After that, the police began to take action. Restore the undercover data and plan to reconnect with the undercovers.

Female undercover A Ding (Charmaine Sheh) received a password invented by Sir Kang one day, telling A Ding that Shao Zhilang (Louis Koo) who sent the text message was the undercover Black they were looking for, but as they came into contact After going deeper, I discovered that Alan (Nick Cheung), who is a brother of Shao Zhilang, also said that he was the Black that the police were looking for. Undercover contact Q Sir (Francis Ng) and A Ding fell into confusion and began to search.