Follow the handbook because thats how the uni has created subject selections for your course. Saves for future clashes if you don't follow the structure.
If your course allows you to choose electives then you choose them at enrolment.
The times are chosen at tut rego. Generally, you do not need to register for lectures, but some subjects might have an execption. You just turn up to the lecture in the first week. As for tuts, you register for them as well as pracs and workshops. However, my course had subjects where workshops were not enabled and workshops were pre-determined based on what course you do. You will discover what tuts, pracs and workshops are enabled on the day(s) of tut reg.