they put it into the reccomended program fo a reason, which is tha some units are only offered in a certain semester e.g. for me business, society and policy is only available in spring.
If you deviate, you may make your graduation a bit later if you cannot complete all your compulsory subjects in time as soem units are only available in cetain semesters. Obivously you can do so, as its up to you, you can change your status to FT/PT, cancel units and change units, and if you are doing so, check the handbook and timetable to see if your cores are offered at which sessions/semesters and then make up your mind.
Usually poeple who do this is to transfer to antoehr course. I changed my units in my second seemster to the course i wanted to transfer into so i coudol get academic credit and not lose time and moeny. Its possible, but there are consequences. You may have to do antoehr seemster to complete in time, maybe not. Just do as much investigation abotu when units are offered and how you can do them in the set time [eg 3 yrs] so you dont waste time] keeping in mind also abotu prerequisites [units you need to do before attempting another] and corequisites [units you need to do simulateneously wiht othe runits].