Why does "excelente" come before "cerveja". I thought the adjective comes after the noun?
Some adjectives can be placed either before or after the noun...some times with a different meaning...
E.g. um homem grande - a big man
Um grande homem - a great man
What is the difference between tem with an accent and without?
Têm is the verbal form relating to the third person plural Eles/Elas. Tem is used with the third person singular Ele/Ela
When you use ter to mean "there to be" (not grammatically correct, but used all the time!) there is never the accent.
Does this refer to two or more people actually drinking (having) an excellent beer (together), or perhaps a bar/restaurant that stocks/serves an excellent beer?
Yes.... maybe they are talking about places (feminine words 'cause of the use of "elas") who serve/sell beer or about the place whose owners are women. So you can refer to the owner when you mean the location.
Why are some accidental typos accepted and others not?
Typos which result in another word are not accepted on the chance that you might actually think the other word is the correct translation.
Not an just a beer