How can we get investigation reports

Hi, This Is vinesh From Hyderabad. My Sister got Married in April 2017 from the very next Month, her Mother in Law and her In Laws Started Harassing her for each and every Small mistakes keeping the Dowry Matter in mind. In February 2018, My sister has been killed and Dramatized as suicide by Hanging herself. But none has seen her body hanging Neither Police Cops nor Neighbours. Her In laws & Husband has created a scene of suicide and taken her to local Hospital, where she Already Died. they Not even informed us about this and we got informed by cops. Prior to this incident my sister was pregnant and got aborted by her Husband's Man Handling. They have been arrested and got bail after few days. But My query is that Now, can we Include another person in this case (with Full Evidences). and is it possible to get Investigation Reports from Police in 304-B Case. some of our well known person are saying that case would have been strong if the Section 498-A also filed against Accused along with 304-B. It would be great help with your Suggestions. Thanking You, Vinesh Kumar