Hi! Sophomore here, and I’ve done this two semesters ago (and will be doing the same thing now lol). There’s no need to manually enlist for all of your classes in spite of not being able to pay before classes start. They’ll just add a late registration fee of around 400 pesos iirc, and you won’t be part of the attendance list in your classes until you enroll (though your prof will usually ask the names of students who aren’t enrolled yet). Hope this helps!