1) Once you have lived in Canada for 1095 days (3 years) as a PR (has to be within a 4 year period), you can apply for Canadian citizenship. Processing takes around a year. You have to pass a test and swear an oath. After getting citizenship, you can immediately apply for a passport.
2) and 3) I have heard that India doesn't allow dual. According to http://www.immihelp.com/nri/dual.html you could get India Overseas citizenship which would allow you to travel to India without a visa but not to vote.
1. Yes, India does not allow dual so if you take Canadian citizenship, you lose your Indian citizenship when they find out. You can apply for OCI (Overseas Citizenship of India) which would allow you to travel to India any time without a visa but you would not be allowed to vote.
2. You first need to have Canadian PR (Permanent Residency) and you must live in Canada for at least 1095 days as a PR (has to be within a 4 year period). If you were in Canada before getting your PR, you can count those days too if they fall within the 4 year period but only at the rate of 1 day per 2 days of stay. The earliest you can therefore apply is either 2 years after getting PR if you had stayed in Canada for a full 2 years before and after or if you did not stay in Canada before getting PR, it would be 3 years after you landed as a PR if you never left Canada in the meantime.