18LPA Senior SWE role offer at hand.

Hey guys, I need your help to make a decision. I recently interviewed for a decent company and they have extended the offer for 18LPA to me I am yet to receive the offer letter over email but yesterday was my salary negotiation round. I lied to them about my notice period of 3 months , I told them it's just 30 days. Now after the salary negotiation HR is asking me to join within 10 days and have even asked for a joining date to be mentioned in the offer letter. Now the issue is I intend to get a matching offer at my current org . And if they don't match it I will have to request for early release but I doubt they will let me go without serving 45 days. How can I steer things from here onwards so that I can increase my current package without having to risk either of opportunities??