Company telling me to serve notice period after resigning and submitting the assets.

I had resigned from my company requesting an early release within a month, which was rejected despite giving all the documents they asked for. I had personal reasons, as I wished to take care of my grandmother after her surgery and look for jobs elsewhere, as I did not see my career growth in the current company. I resigned stating that 13th February 2023 would be my last working day and I would hand over the assets and I did the same. They kept asking me to serve the notice period which I told them that I would not be able to and can instead compensate with a buy-out, which they rejected too, and when I informed them that it is stated in my Offer Letter that I am entitled to a buy-out, they told it is at the company's discretion only. They sent me a show cause notice, stating the company needs me to do my work on the projects but I never was assigned to any project I had been on the bench till the very last stated day of my resignation. I informed my manager and HR of my intention to not continue working and that I would rather compensate for the next 2 months of notice and I want my relieving letter. What can I do in such a situation? And can the company sue me? I have tried my best to request them for letting me buy-out but they denied it, so what should I do now? And how should I reply to the show cause notice?