Earlier quoted context omitted.
2) I don't believe so. 3) The hope is you don't have to use an intermediary coin.
They have declared that they will not access the data. However, Facebook makes extensive use of shadow profiles of people who aren't even Facebook customers. They could certainly add Diem blockchain data to those, as they will have access to said blockchain via Novi, their Diem wallet. David Marcus and Mark Zuckerberg have both stated that data from Novi will not go to the Facebook advertising engine. However, Zucker…
That being said, there is a lot of work being put in making sure that FB doesn't have access to Novi user data. Of course, sometimes one employee's mistake can lead to infringement of a claim, so to avoid that good frameworks have to be put into place.