Gwen Robbins Schug
No. These are questions that have not been tested scientifically but there is no evidence to suggest that there is reason to believe these were features of Indus life.
Jonathan Mark Kenoyer
So far there are no depictions of people being bound or captured. Slavery however is something that can occur without overt depictions so there is no way to determine if there were slaves in the Indus cities or not.
There is only one depiction of a human head placed on a stool or low table in the famous seal from Mohenjodaro that depicts a deity standing in a pipal tree. A man with a horned headdress is kneeling in front of the deity. A giant ram and seven figures in procession complete the narrative. This scene may represent a special ritual sacrifice to a deity with seven figures in procession but it is not certain if the human head is the sacrifice or if it is the head of an ancestor that is being ritually presented or honored (Mohenjo-daro DK 6847, Islamabad Museum, NMP 50.295, Mackay 1938: pl. XCIV, 430; pl. XCIX, 686a, shown above).
Rita P. Wright
Above: Diety seal, Mohenjo-daro