At least for Toronto jurisdiction, it is not mandatory. As per the checklist, if you have not applied for canadian passport, you can write a declaration addressed to the Consulate General stating that you have not applied for a foreign passport, and hence don't have one. Can't comment about Ottawa and Vancouver jurisdiction.
Personally, I would strongly advise that you wait until you get your canadian passport before you apply for surrender certificate. BLS is notorious for asking for documents out of the blue, and deviating from the standard procedure will only worsen your experience with them. Which is horrible to begin with.
https://www.blsindia-canada.com/trackapp.php
For application type, select Passport Application.
Sorry, I don't have answer for this as we applied in person.
I do advise applying in person if possible as once they accept your application in person, it is pretty much guaranteed to be processed, whereas in postal, there is always a chance they might reject it for a random reason. To book an appointment, visit this link between 8:30 am and 9:30 am daily. Toronto and Brampton same-day spots show up in that timeslot and you can select any type of appointment (Visa/OCI/Passport).
https://www.blsindia-canada.com/appointmentbls/appointment.php
Just my guess, but knowing BLS, they'll ask for a 2nd appointment as well (OCI checklist is very long and I think it takes a long time for the person at the counter to verify the documents). Who knows?! Maybe by the time you go next week, India opens eVisa for canadians (I think India removed canadians from evisa eligibility as a retaliation for Canada having specific testing requirements from India - which was removed last week).
Alternatively, you can try booking a same day appointment using the steps I mentioned above to another person.