A: Yes, I think you can get Lady Luck DS again in Chapter 5 if you challenge Shinra to a Sphere Break battle, but the odds of you winning are greatly reduced from that of the Sphere Break battles in Chapter 3. If you cannot beat regular people then I suggest you practise a lot, as Shrina is a very tough opponent.

B: You can fight anywhere that isn't marked as a hotspot, as it is only these missions that advance the storyline.