Termination law

hello everyone,
I want to ask a question regarding an educational providing company basically an institution. The company has terminated an employee and also refused to pay his salary of 3 months which was continuously being delayed by the company from last 1 &half year. The company never paid the salary on time. The reason of terminating the employee was that he had some data of the company saved in his personal hard disk and he was also found guilty for giving private tutions to the in-house students of that particular institution.

The company also asked the employee to pen it into paper and sign it that he is guilty of the tasks he has done ie.providing private tutions and keeping the company's data.

I want to ask you that is this a crime  and if not what actions could be taken and how can he get back his 3 months salary.

Tell your answer according to Indian Law