Can brass bugle play Amazing Grace?

No. Bugles are very limited in the number of notes they can play. The variety of low range notes required to play Amazing Grace would be impossible for a bugle.

Jason -- have you *tried* it yourself? I've played a version of "Amazing Grace" on a US Regulation bugle that was recognizable to people who were not told in advance what I would be playing. Think of it like bagpipes or carillon -- true, the bugle only plays a few intervals, rather than the full chromatic scale which most musicians are used to. But listen to how a bagpiper will work around the "missing" notes to make a tune succeed despite that.