Detective agency's evidence

Dear Sir/Ma'am

Kindly look the below story and provide the suggestions.

Background:-
Our marriage has been solemlised on Jun 2011 by the marriage register and wsocial marriage has been done with the presence of both the parents on Oct 2011. During this relationship we have a baby girl whose age is now 8yrs. All of us belongs from Muslim family.

Story :
On May 2016 498A has been lodged against me and my family, but no such movement seen till the time of this case, not only that also commitment has not been done.
in 2016 DV has been lodged which was dismissed fordefault on 2019.
in 2016 MR 125filed and same has been dismissed for default on 2019.
In 2018 Mat suit for divorce has been filed and withdraw by the petitioner(wife) within 15 days from filling.

My side :
in 2018 RCR has been filed which is in exparte hearing stage.
in 2018 Custody of Minor child has been filed also the same is under ex part hearing stage.

Now we came to lernt that from the reliable source and few voice records of my wife where its has been clear that she is living immoral life such as illegal affair with a boy whose family background is also bad.
most of the time this gentleman has come and stay at FIL's home with my wife and wife also night staying with her boy friend at his residence.

This gentleman has also convicted with so many criminal cases like 498 and others from his 2 wife's. All the cases is in investigation stages.

My views and qury:

If I appoint a licensed holding detective agency to captured their all activities and if that agency will provide their statement as both of them already engaged in illegal illicit connections and the atmosphere of their livelihood is not good for a baby girl then should I get the full custody of my baby?
Detective agency hired and their report is legally accepted in court room?
kindly suggest.