how to reply the legal notice on following points.

according to normal company rule if you leave the job without a notice period, you will have to pay a penalty like the salary for the remaining days..... for example- suppose you left on 15th , then the salary from 15th till 3oth you will have to repay back to the company.....and if you do not  they can file a FIR against you for criminal case that you have to face. 

You are yourself an advocate and you should know what action you can take. Did you join the company as a legal adviser? You have not mentioned anything about the nature of your work,  the terms and conditions of your employment and the basis of their claiming Rs.73000/- from you. Without knowing details no advice can be given.

Hello sir!

It depends upon the agreement between you and the company. If it states in the agreement that you have to give a notice before leaving the company, it becomes necessary to do so. Indian courts give more importance to the written agreements or contracts between the parties and if it is mentioned in your agreement that you have to serve a notice period, then the court will implement the same or they can ask you to return certain month's salary back to the employer.