Termination By Employer Saying Absconding

I was working with a company for more than 4.5 years and even worked in second shift till 10 pm in night for about 3.5 years I had a good performance record in all the annual performance reviews.I had some health issues and was on leave this was informed to my manager and HR.After I joined back my company asked me to work in 8 AM shift which I did not feel feasible as I had just recovered, HR asked for medical certificate saying I am not able to work in 8 Am shift my employment letter does not have any clause saying I will work in any shift still they blamed me for not being flexible and said this is my last chance. I again felt not well and went on leave within one week HR sent a mail saying respond today and before I couldsee the mail on next working day itself dropped another mail saying we have initiated termination and in few days I got termination with no show cause letter received and now after 3 months company asking for notice period recovery I did not resign I was terminated without any notice and still they are asking me for notice period amount and they have not even given my experience or relieving letters which is making it difficult for me to get another job Can. Anyone please advice what i should do in this case

From your versions it seems:
1. Your termination is illegal. If you fall under the category of 'workman', you can seek relief from labour court/ industrial tribunal and will be entitled to reinstatement with back wages.
2. Company cannot claim notice pay since they have terminated your service.
3. If company sends you any notice/ letter, always reply them with assistance of a lawyer, if required.
What I can say that you have a good case for challenging such termination. If you wish to challenge, do not sit idle.

I do not fall in workman category. I want my documents experience and relieving letters so that I can get a new job and also as per the offer letter if company terminates me they are entitled to pay me 3 months basic pay so how can I get this amount Also how much would be the cost incurred for legal proceedings

If you do not fall within the category of 'workman' then seeking remedy can be expensive as well as time consuming. You have to approach the High Court in that matter, I believe.
Cost of legal procedure depends on the seniority of the lawyer as well as your geographical location.