Is it compulsory to have Faculty Advisor? What should I do if all our teammates are graduated?

Yes, it is compulsory. If you have graduated, you may find your previous professor / lecturer / instructor as your Faculty Advisor. The faculty advisor serves to confirm the eligibility of the team members and the integrity of their business plan. Ideally they should be a teaching staff (e.g. Professor, lecturer, instructor, etc.) of the tertiary institution, who may advise the team on idea inception, venture plan development, conducting market research, recruiting strategic partners, etc.