You generally can renew items. It is best to renew them before the due date. The lending library may grant or refuse a request for renewel depending on demand for the item at their library. You will be informed of the lending library's decision. If the request has been denied, the material is due back on the original due date.
Interlibrary loans are available most of the academic year.
Copyright law does apply when making photocopies of copyrighted materials. Materials intended for any purpose other than private study, scholarship, or research. You may be restricted to a certain number of requests per week, month, or quarter depending on how busy the interlibrary loan department is at that time.