Here are my answers:
1. If you ask, they say :) Meaning that typically they have a few data that are going to give you right at the start. But they also have other data that they'll show you if it fits within your structure (maybe the case goes in a different direction and there is no more need for that data) or they'll show you if you mention that specific piece of information (e.g., we would need to consider the target segment for our client, do we have any info on that? Yes, in fact, I have here the table...). Usually, if you are not mentioning that info but it is vital to go on with the case, they'll try to help you "say" it
2. Well, it depends. If your framework is always wrong when you start and you need me to re-focus you on the right path, that's a "minus" on your side, thus you have to be sure to be good in the other parts of the case
3. The interviewer can totally understand when you are stuck. The good thing to do in these cases is: talk so that the interviewer understand where you are stuck, what it is that you are missing and can be able to help you to go back on track. If you remain silent, staring at the blank page, they wouldn't be able to help. Also, clearly say: "I'm uncertain of this" but be sure to provide a few alternatives "..because I'm considering this, but I'm not sure if it's applicable in this case for this and that reason. Thus maybe I could go from this way to calculate..."
4. 1 is fine as long as it's short, 1 sentence max. The case is 20-30mins long, you can bet I remember the client's situation. 2. three is the magic number in consultancy, 2 is bad, 4 is good, but 3 is perfect. 3. Invert 2 with 3, consultancy is all about top-down communication, before the answer and after the back-up, not the other way around. 4 and 5 great
5. Top-down communication is better, as mentioned above. I know it sounds strange because for example from university, we are required to state all hypotheses and proofs and then draw the conclusion. Consultancy is the other way around. Thus, I would advise saying "I would investigate areas 1, 2 and 3, looking at costs and revenues in all of them". At this point, the interviewer would have the chance to tell you "ok, let's focus on 2" and then go ahead. If they don't say it, then "In area 1 I would investigate a,b,c,d, and e". In area 2 "...." and area 3 "...."