Congratulations on getting your first client. Unfortunately, I can’t offer any help with your questions, but thought as you hadn’t had any replies to your query I would at least make a comment.
I am considering applying for a practice licence, but am worried I will end up in a situation like you where I am being asked questions that I feel out of my depth with. Despite passing my level 3 and SAT courses with great grades I just don’t feel confident enough to go it alone.
I appreciate this is no help to you, but at least you know someone understands your current situation. Good luck