Chief Burleson indicates her intention to interview Alma alone. Police cannot normally interview minor children alone. Parents have a right to be present to guard the interests of the child. In cases where that may not be appropriate, such as the child being a potential witness to crimes committed by the parent, a professional such as a lawyer or social worker should be there to guard the interests of the child.
When Harry answers the door, Chief Burleson barges in. Police normally need permission from the owner/resident to enter a residence. They can only enter uninvited if they have a warrant or if there are exigent circumstances, such as pursuing a fleeing suspect or responding to evidence of an imminent crime (such as screams, etc).
When Harry is taken captive Melanie tries to get him to take Viagra before forcing him to participate in Tony's snuff film. However it is a common misconception that drugs like Viagra will always cause an erection on their own. A man still needs to be sexually aroused and stimulated to get an erection even with Viagra, the drug will not cause an erection for someone being forced to participate in something that doesn't arouse them.