Is it legal for employer to seek buyout option on gross salary?

I am currently employed in a reputed & listed travel company headquartered in Mumbai and have resigned on email with a copy to my reporting manager & concerned HR. As per my agreement with the company & my current designation, the termination clause is as follows "The Management reserves the right to terminate your appointment at its absolute discretion, after giving you three month's notice or on payment of three month's salary in lieu of notice. Similarly, you shall be at liberty to resign from the service after giving three month's notice" However, I will not be able to serve this period and would like to have my notice period shortened to 30 days as my new employer won't wait for me until then, I have got no acknowledgement on email about my resignation being accepted, But I am constantly in talks with my manager & HR for my notice period waiver. As per the company's exit policy that was shared by HR, i am supposed to pay 03 months GROSS salary (and not basic salary) to the company. Is this legal? Added to this, I can't even adjust my pending leaves in lieu of my notice period. Is this in agreement with law? Also after my resignation, I am not entitled to any leaves. If I take a leave, then the company will cut my pay for that particular day. Again is this legal? For the year starting Jan, I have just taken 03 leaves and even if I calculate on pro rate basis for 06 months, I am eligible for a minimum of 15 leaves. Would be highly obliged if I receive an advise on my above mentioned problem. Thank you!