I am not totally understanding of the way downloads work. But to my knowledge downloads go directly between the uploader and downloader, not via ultrapeers. Once someone begins a download, they become directly connected to the uploader to my knowledge.

If you used LW 4 you might have been aware of the Direct Connect search option. I believe downloads work in same fashion as DC. (DC search function was restricted to 'Friends' in LW 5.)

Ultrapeers help people to connect to the network. They are also the search hubs. They act as go-betweens for searches and help distribute searches.

Search results I am not sure about how they work.