TRV - Application fee, flight booking and photograph

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Hi,

My mother in law is applying from Bangladesh for TRV. I have some basic question about application process.

1> Does the application fee needs to be paid before application submission to VFS. Or should it be paid at the vfs center when submitting the application?
2> Is flight booking information needed for TRV application?
3> Is there any need to take photograph for the application or will it be cover by biometric process at the VFS.

Thanks.