1. you can apply for passport the same day as at the time of ceremony you get your citizenship cert.
2. if you want to apply for oci then you need to submit your passport back, you need to contact indian consulate to get that info on where to submit your passport, make sure you keep copies of that.
3. yes they charged me like $250 to surrender my passport.
4. you can right away apply for OCI after you get your canadian passport, I got mine in 6 weeks, i am in calgary, they dont do PIO card anymore, and they dont have any expiry dates. it says lifetime visa