Buyout

Hello everyone! My notice period is of 90 days and in my offer letter it is written like " After confirmation notice period will be 3 calendar months or payment of 3 months Basic Pay in lieu of notice. In the event of your decision to leave the organization after confirmation by payment of 3 calendar months basic pay in lieu of notice, you will be required to complete the pending work in your assignment and submit a satisfactory hand-over of your responsibility, prepare a proper knowledge transfer documentation being subject to acceptance by organization, to be eligible for your final release and final settlement." My questions are 1. Can my current employer restrict the buy out period, like notice period is 3 months salary so can they say that its compulsory for you to serve notice period for one month and you can buyout only for 2 months. complete buy out is not possible. 2. If I buy out for all the three months so can they deny from giving me experience certificate? 3. If they force me not to buy out what actions I can take against them? 4. After buying out for 3 months if they donot provide me experience certificate then what is the law for that. What I can do in that case. 5. I spoke to HR of my current employer they said that even if it is written in offer letter I can't do the buyout . They said that if I don't serve the notice period then they will not provide me a experience certificate. They will not allow me to do the buy out. Is this possible? Please help me out of this. Thanks