1. No , not at all, they have to follow what has been in terms and conditions of the appointment and you also, if you want to buy out you can.
2. Why , they can't they have to issue these documents.
3. First join another company if joining after submitting conditional resignation then ask for the clearance of the dues, if they don't agree , then give a complaint to the Labour Department under ULP.
4. Nothing, if they start this is harassment then also file a complaint against the company with the labour department.