Does USPS delivery confirmation require a signature?

That depends on what the sender chose, I know fedex and ups will just click a signed for button if nobodies home, and when you go online to tracking to shows up as signed for (unless sender specified that actually counts as delivered for insurance purposes, we had an issue with an ipod that never showed up), I beleive once they click that button it takes a gps stamp, so if you say it wasn't delivered they will say well our guy dropped it off on your doorstep.

It depends. Usually the shipper (whoever you bought it from on eBay) can choose if you need a signature. I've gotten packages via delivery confirmation and most of the time they didn't require a signature. Sometimes they just leave the package out by the door. I don't think it will require a signature, that's usually for bigger/more expensive items.

Usually no signature require unless the shipper requires it which it would say on the tracking number but i yours doesnt say nothing then no signature require and if the mail man feels that the package would be safe outside your house he will leave it there but if not he will just leave a note for you to pick up. (in case nobody is home)

Yes it does most of the time. However once the guy just put it near my door, but usually someone will have to sign, not necessarily you.

Delivery Confirmation is just the USPS way of saying online tracking. No signature is required. It would then be called Signature Confirmation