Relieving & Experience letter

I am currently working with a MNC Limited company, I resigned on 26.8.2022 through the employee portal(also sent mail to both reporting manager and hr), stating that I will be serving my notice period of 30 days upto 25.9.2022 - in the same mail I also requested to be relieved early by 2 days if possible, as I have an early joining at the next company. 1. I am planning to use the buyout option for 2 days if I am not relieved early, can the company refuse to give relieving letter in that case. 2. Yesterday my reporting manager's manager (department head) called me and said he is willing to relocate me anywhere I wish to go and also match my salary to the offer received - I did not no what to say at that time (although I was clear about leaving did not state that on call as I was surprised by the offer) - told him that I'll let him know in 2 days time - will this effect my notice period duration - i plan on calling him in 2 days and stating i still do not want to stay. 3. My company has a history of holding employees beyond the notice period by giving more work - is that leagal what can I do about that in case that happens as this could lead ruin my career as I would lose the job offer in the next company.