apple sandwich? :p

Or a nice picnic :D

Not to mention, one heck of a party.

Plate sandwich sounds yummy

The word хлеб as a type of food is uncountable and so has no plural. The word хлеба (а is stressed) exists, but means "grains (growing in a field)".

Yes, there are two forms, хлеба and хлебы, but first means "grains" while second means "loaves of breads"

In english its either a loaf of bead or just bread

Oxford comma is for English, not for Russian =) When you make a list of something in Russian, you should never use oxford comma, because it would be a mistake.

That one got me as well.

Forvo.com says its as Duolingo says, although I don't know the credibility of this audio.

The pronunciation here is so bad it is the first time I actually report it.

You've got it the other way around. The difference between 'a' and 'и' is that 'a' is used when a contrast is implied (think of it as a soft 'but'), whereas 'и' is used when there is none. For example you would use 'a' in a sentence such as 'My mother is a hairdresser, and my father is a mailman', but you would use 'и' when listing or joining up things.

Hope this helped!

I think it is because they are making a list of what they have, and regardless of the nature of the stuff being mentioned, when listing items you use и. That is what I have understood so far.

You use а when there is a slight difference. Think of it as a soft "but". For example:

Я - девочка, и она - девочка. (I am a girl, and she is a girl.) Я - девочка, а он - мальчик. (I am a girl, and(but) he is a boy.)

Please correct me if I have made a mistake!