Can this fixture be attached to a recessed wall mounted standard size round electrical box?

Yes, it could. BUT......that is not recommended. doing that will mean that the total weight of the fixture will hang on the two VERY SMALL screws that hold the cover to the box.

No It can not... I just installed mine and to my surprise it wasn't designed to be installed directly to an electrical box. I had to put a junction box over the existing electrical box and then run conduit from the junction box to the light fixture. I wasn't happy about this method of installation and had I known that at the beginning, I wouldn't have purchased the light.

Not without an adaptor of some type. And it is too heavy for a standard box.