Is medical leave denial and BAMS certificate valid under law?

Joined a factory on dec 2023. Till date factory not issued me any offer, appointment/ joining letter. I have no formal contract. I resigned on 1 sep and serving notice period till 30 Sept. Unfortunately, during notice period I have fallen ill due to infection and doctor advised bed rest during treatment and also issued medical certificate for the same. But HR refused to grant me any leave even for medical reasons and also made a threat that in india medical certificate issued by BAMS degree doctor is invalid. Now question arises:- 1. Whether employer did justification for me by denying granting of leave for medical reasons? 2. Whether medical certificate issued by BAMS DEGREE DOCTOR is invalid in eye of law as guided by my HR?3. Whether it is compulsory for me to complete 30 days of notice period inspite not having any employment contract?4. What documents do I need to collect from employer or it is feasible to have reliving letter in absence of another appointment documents?