This is MRP. You will likely remember this from Level 4- it comes up again here but there's nothing new that you won't have seen before. P.55

This is Quality Function Deployment. It's a framework for ensuring that products are designed in line with what customers want/ need. P.112

4 is the only strategic decision listed here. The other options are 'operations decisions' rather than 'strategic'. Strategic decisions influence the direction the company is going in and may have an effect on the long-term strategy of the company. Operational decisions are about ensuring everything runs smoothly and the Five Rights are achieved. This is from p.4-6 of the study guide.

The formula for working out gross profit is (revenue - cost of goods sold) divided by revenue. Therefore 2 and 3 are correct. It's unlikely you will have to do any mathematical calculations in this exam, but if you do they'll be super easy and there is a calculator inbuilt into the system you can use. There's a couple of different cost formulas on p.78 but these will be familiar to you already from Level 4.

They're known as black belts (yes, like in martial arts). To gain a black belt in Six-Sigma you usually have to undergo a training course and have so many hours experience. See p.139.