I was there today too, got 20/20 and was the first to leave the test haha.
The officer had the citizenship application printed (at least some), because I saw the photocopy of my English test certificate. They didn't ask to see a language certificate, but it seemed like she was asking me questions (why did you move around, etc) to test my English.
She looked at dates on the stamps to prove entry/exit, it was really quick, I doubt they would care about translations of those.
Do not provide or show what is not asked, keep in a folder.
About 20-25 people were taking the test, and I thought it was gonna be on a computer, but it was on paper (multiple choice, still), using a pencil.
Nothing to worry about with regards to dress code, just clean and tidy.
She said the ceremony might happen at the end of September, otherwise October 4th, and that I could vote by calling the Elections office