How can a PR holder 18 year older, study MBBS 5 years in India and maintain PR... Will mother taking Canadian citizenship and showing student is financially dependent on mother help,? Any permission to be taken by Canadian education system,?
The short answer is that there is no way they can do this.
If they complete 5 years of studies outside of Canada, they won't meet the residency obligation and there will be a significant risk of losing PR.
No, the mother taking Canadian citizenship and showing the student is financially dependent won't help. By the time the student completes their studies, they will be 23 years old and an independent adult in IRCC's eyes.
No, there is no way to get permission.
If they pursue the 5 year program outside of Canada, they must be prepared for the possibility they may lose PR.
If they don't want to lose PR, then the studies should be completed in Canada.