I am applying for Chinese visa (mainland), do I need a bought flight ticket?

Hi guys,

I am applying for a Non-Business Visit (F) type since I am going there for a conference.
I have the invitation letter and the support letter from my university. However, apparently I need to show hotel reservation and flight ticket.
Do I really need to buy the ticket? What if I show them only the flight time (page screenshot from Kayak)?

One more thing, the conference secretaries advised to apply for a tourist (L) type tinstead of F? Is there a significant difference? What would you advise?

Thanks.