Company is not accepting my resignation

Hi, I'm in a situation, I got an excellent opportunity from MNC. So after getting an offer from them, I resigned from my current company on 2nd Jun, my new company wants me to join them on 24th Jun, so I resigned requesting for early reliving. Then the HR manager told me verbally that inform the new employer that I'll have to serve the full notice period and I did the same. I got extended notice period so that I can serve the full notice here but now still they're not responding to my resignation, I talked with my manager multiple times, who is also the director of the company, but he is not ready to accept it, ignoring me by saying I've more important work, will see this later. You've to complete the project and I'll relieve you based on its progress, kind of harassing me mentally. My official notice period with the company is 30 days. They're threatening me with the clause mentioned in my appointment letter that says "You may not leave the Company in the midst of a project, without proper handing-over of the project. An absence of more than week from work without notice will be treated as an unqualified resignation from work on your part against the spirit and letter of this contract, allowing the Company to initiate any legal proceedings as per terms of this contract." My future employer also wants to get proper relieving from my current company, so I can't have any issues during BGV. Can I leave the company after serving full 30 days notice period, Can they something against me If I did, and can they hold my experience and relieving letter because I want to leave doesn't matter whether I'll get new job or not. because now I want mental peace. Please guide me, I am on a bridge that is burning from both end.