You may choose to defer the start of your study until Term 3.
Your COE will be cancelled and you will need to accept your new offer. Once you accept your new offer a new COE will be issued.
You need both a valid COE and visa to enter Australia. Your student visa should stay in place.
Please check the Visa Entitlement Verification Online(link is external) (VEVO) system for your visa end date, updated details and conditions.