After the completion of B.Pharm course, is it okay to use the suffix DR. before name and can open their own clinic?

No, B.Pharm degree holder cannot use the prefix "Dr." nor open a clinical practice to diagnose/treat patients. The "Dr." prefix is approved by the Pharmacy Council of India (PCI) for Pharm.D graduates, not B.Pharm. B.Pharm graduates are licensed pharmacists, not medical practitioners.