I had to learn answers to the 100 questions for the citizenship test:

And you now probably know more than at least half of natural-born citizens.

When 1poorlady was getting ready for the test, we had a coworker who was very knowledgeable. We already ate lunch together almost every day anyway, so when he learned she was going to prep for the test, we started talking civics and history (US). Using smartphones to clear up any uncertainties. 1poorlady aced the test. We probably over-prepared her, since it was the better part of a year that we did this almost every day at lunchtime.

Back in those days we had to file all the paperwork by US Mail. There was very little online at INS (which is what it was called then, before changing to -IIRC- BCIS, and now USCIS). I remember having to go downtown to visit the INS office to pick up required forms (it was a half-day standing in line, most of which was outside in the AZ heat). If there was a sample test, it would have been paper mailed to us. It's been a long time, but I think they mailed a booklet with some basic knowledge. We prepped her far beyond that. :-)