Q1. This is the standard recommendation we give: "For Big Blue Button, especially for the moderator to use presentations etc. it is recommended to use the latest versions of either Chrome or Firefox. Safari will not work, also older versions of Edge will not work." (from https://community.onschool.ch/t/big-blue-button-browser-requirements/73)
Nobody has contradicted this so far.
Q2. Do you mean, that the participant uses a smart-phone as the client device, not a laptop nor a desktop? And what is the problem you've observed when they do?
Q3. You can't just throw "Mac devices" in to one item. There are many different hardware (iPhone, MacBook, PowerBook, ..), different operating systems (Mac OS, iOS) and different browsers (Chrome, Firefox, Safari,..). You have to be more specific and describe the problems separately.
I see that you are not the administrator of your school's Moodle nor BBB server. Did you talk to them?