Yes, After landing and starting PR process, I'll fly back to India and join back my current job.
It is under assumption that
1. I will not be able to search for job till I get SIN / PR Card.
You will most likely get the SIN number the same day. Only a matter of minutes. I don't think you need a PR card per say to find a job. As long as you have your stamped COPR with you, that will act as proof of status till you get your PR card.
2. I'll get single entry visa from express entry, I'll fly back to Canada only when I get PR.
Not necessarily. You can fly back to Canada using a one-time "Travel Document". You can apply for this travel document at the Canadian High Commission, Delhi. You need not wait till you get your PR card to travel back.
3. I have to land before my meds expire or get new meds done and restart the process.
If you DO NOT land before your meds expire (or your current passport expires, whichever comes first), you cannot just re-do the meds and land again. Your COPR will most likely will be invalidated and you cannot travel using it. You have to start the process FROM SCRATCH. So, unless you have an extraordinary circumstance (Death of a family member {God forbid} or any other extremely compelling reason, do not try this - It is NOT worth the risk. There is no guarantee that your new application will be approved , do NOT waste the opportunity.
Please correct me if I'm wrong.