Can employer stop the relieving/experience letter

Dear All I have resigned from my current organization on 1st March 2021. I have requested manager and HR for early relieving and mentioned my last working day as 24 March 2021 on mail. In my offer letter notice period is of 2 months (60 days). Offer letter having following line "if you chose not to serve the notice period the company reserves the right to recover competition in lieu of notice period from you." Now HR saying she needs business go ahead for early release after evaluating the business requirements without that we will not be able to process the same. When I spoke to my manager he is not ready to release me early and told me he can only adjust my balance leaves which are 14 and I need to serve till 15 Apr 2021. When I spoke with HR for this as manager is not ready but I can not continue after 24 Mar 2021 she threatening me as then we will consider your case as absconding. I have done knowledge transfer to team and no pending issue currently with me. Same I mentioned on my latest mail to them. I have already communicated on mail as I am ready to pay compensation in lieu for unserved notice period. They have not yet replied to my mail nor they accepted my resignation. I have joining date as 25 March 2021 with my new organization. They want my existing company relieving letter as a background verification documents. I have couple of questions regarding the same. 1. In this case if they do not respond to my mail can I stop working with them from 24 March 2021 and join the new company from 25 March 2021? 2. Can I get the relieving letter as I am ready to pay them for my unserved notice period? 3. If I send them chaser mail on 24 March 2021 stating as I have not received any response on my previous mail I am considering this as acceptance of my early relive and I am not login from tomorrow. Please communicate further on my personal mail ID. Will this stands as a legal proof?