How to go about getting Visitor visa at Calcutta consulate

Hello Everyone,
My parents, residing in Ranchi (Jharkhand) have to apply for visitor visa at Calcutta Consulate.

My queries are:
1> They cant use drop box coz of age restrictions, so whats the procedure, do they have to go to Calcutta personally to submit all the papers to TT services?
2> Will TT services review the documents and tell them abt missing ones and then give an appointment time to them to appear at the consulate? Or they have to take an appt on their own from web?
3>Or they take an appt from web directly to appear before the consulate with all the documents?

I would be thankful if someone cud kindly reply to my queries