Our school uses the ERB-CTP-4, and the description of it being a "reasoning/achievement" test is fairly accurate (imo). I think that the best way to determine how long the test will take and how often breaks are given is going to be to ask the school (or other wherever) that will administer the test, because the ERB comes in parts, and how long it will take is going to depend on how many parts are administered. The test is given at our children's school over three days, and I think each part of the test takes around 2 hours for the typical student (I don't know this for certain because I've never been at the school during the time it was administered, but am going by what my kids have told me - and my ds, fwiw, has finished some parts of it in much less than the time given, but also used the full time on other parts). I am fairly certain that during the several hours the test was administered on some of the days, the students were given more than one subtest.
The test answers are written on a bubble sheet at the level my kids are testing at, but they are older - I don't know how the answers are given in early elementary grades.
My kids have also taken the TerraNova and in general I'd say the two tests are similar in what they test, but I don't know anything about the format of the questions on either. I'd be surprised if you could get sample TerraNova questions - I think they are held very confidential as well.
Best wishes,
polarbear