gulzar ji started this thread and left after he got his visa..i will answer questions that you have asked him, if you don't mind
1. if you are a canadian PR, you can stay as long as you want after you, as a sponsor, have been approved based on eligibility criteria. However, if you are a canadian citizen then CIC would want to know if you are planning to permanently live in India. You can show them that you had significant ties (owned house; letter from landlord saying that you have agreed to move back to his/her house after the visa approval process is over; job offer when you go back...things like that)
2. No they won't question unless you are a citizen. If you have met your PR requirements then you are free to live in India (say you just renewed your PR card then you have five years validity. Before it expires, you must have stayed in canada 2 out of 5 years to meet PR eligibility)
3. you both can go back together (if the canadian immigrations asks then you can tell them you had decided to stay back until your spouse got PR visa)