Is return ticket required in advance for S2 visa type ?

Ankur, you don't need to book the return tickets in advance. The process is simple. First, prepare all documents that may be required, including your mother's passport, passport copy, a filled-out application form affixed with her photo, an invitation letter from you, your birth certificate, and a copy of your passport and residence permit of China. Then hand in the application to the embassy.

Thanks a lot Fanny