Alexander makes a good point. We really don't KNOW anything. However, from what I've seen, people who have taken the test said that their video question (if there was one) was at the very end of a block. I think it's likely that video questions are experimental at this point, since they have not previously been used on the exam. I'd speculate then, that all the experimental questions are at the end of blocks. This makes sense because if students don't get to the experimental questions, or take too long on them, it should not impact their score, which is the intent of these questions (to test them out under live test conditions without adversely impacting the rest of the exam).
Even if this theory is true, whether the last question in every block is experimental, or the last 3, or only questions in certain blocks is anyone's best guess. Unfortunately, you have to put the same effort in to those questions as all the rest.