There's a difference between en öl and ett öl. En öl is a glass (ett glas), a stein (en sejdel) or some other unit of beer intended for consumption. The kind of thing you mean when you ask for "a beer" in the bar. Ett öl is a kind of beer, like in "this is a good beer" or, [insert your favorite brand here] is a good beer.
Yes! Norrlands guld is the only one that comes in my mind straight away, but there must be others. And we call them by name like "Carlsbergs", "Heineken" and others. You can also order "En stor stark" it means a big glas with strong beer, kind of, but it's probably about the % in the beer anyway you will get what the bar has in there tap at the moment.
This might differ depending on the type of English you speak. In American English, "a beer" sounds totally normal, and the phrase,"Would you like me to grab you a beer?" is said several times a week in my household. ;) Conversely, most English speakers outside of America seem to say "an ice cream," whereas that sounds odd to Americans (we don't consider it countable).
To have a beer or even a few beers is totally normal in British English (and in Britain ;-)) as well.
Haha, nice. What's happened is that Duo will allow one typo per word, as long as that doesn't turn the word into another actual word. So the lack of space counts as a typo towards en, and the extra e counts as a typo towards öl, and it thinks ö and o are close enough to not count as typos. :)
Depending on whether you're taking about 1. a serving of beer or 2. a type of beer: A beer"= 1. "en öl" / 2. "ett öl". "The beer" = 1. "ölen", 2. = "ölet". In definite form you don't have to distinguish; both work for both: "Many beers" = "flera öl"/"flera ölar". "The beers" = "ölen"/"ölarna". ("ölen" used the same as "träden"="the trees" in this example)