OTV Multicast Transport and IGMP

Before I implement OTV at a customer site, I wanted to ask if someone could clarify the following concept for me. The AED device, N7K VDC in the planned implementation, uses the site VLAN to create dual adjacencies with the other edge devices in the site and remote site over the join interface so that the control plane can flood the information pertaining to MAC reachability. In order to facilitate this we all know the edge devices use any source group to facilitate this communication using IGMPv3. What confuses me is

1. why is IGMPv3 required, as it seemingly is explicitly listed in all the documentation I read.
2. Which device facilitates the IGMP querier role which manages the membership report database, in this overlay network. Is it the AED's or is it every Edge device in the overlay network?