Science does not require a minor. However, you do need to do an approved Level 1 sequence as part of the "Science Specified Study". You should check that you fully understand the requirements of the "Science Specified Study" section, as it's quite specific.

I think you can convert the Level 1 sequence into a minor by using two of your electives. However, this is something you should discuss with a course adviser / Science Student Services, as information is limited online.

You can do electives from anywhere that will have you. So, yes, in theory you can do music or philosophy. However, some faculties restrict enrollments to only students who are enrolled in a degree in that faculty.

Your best resource for understanding what you can do / must do in your degree: the Bachelor of Science Requirements.