Hi guys,
I'm in process of applying for a visitor visa, and instructions posted on UK border agency's website are kind of confusing. I hope I can get answers to some of my questions here. Plus I'm tired of calling up WorldBridge and spending $3 per minute ...

Is the photo just like a normal 2x2 US passport photo? Something I can get just by walking into a Walgreens?
For the return service, I was told by WorldBridge services I need to provide a envelope or a box along with a "electronic prepaid way bill". Not a prepaid label (self addressed and stamped). What the heck is a electronic prepaid way bill??? I called up UPS and FedEx, and they have no idea what is this thing. They told me they probably meant prepaid label is what I need, but I was told over the phone explicitly they want a electronic prepaid way bill!!! I have no idea where or how to get this thing.
Does the flight have to be booked? Or can I just print out a a planned flight?
Do I have to submit my actual green card? This thing is not cheap, and I don't want lose it.
Much thanks!!