Company not returning security cheque

Hello, I joined a startup IT company on 17th Feb, 2015. I signed a bond with the company which says that I am not allowed to leave the company for an year, and that I can only leave after one year by serving a notice period of 45 days or paying the equivalent amount. They also made me give them a security cheque of Rs. 40,000 (@ months salary). I wrote the amount and signed the cheque. The date and name were filled by the employer. The quality of work here deteriorated and I started to look for another job. I interviewed and bagged a far better job with a reputed MNC, but they were asking for a immediate joining. So, I put my resignation and decided to leave. I dont want any kind of relieving letter from them. Now they are refusing to return my security cheque despite the fact that I am ready to buy myself out by paying the amount according to the notice period served. I resigned on 31st August and they are withholding my salary a well. Now the catch here is that the bond that I signed was on an A4 size printout and I did not sign on any kind of stamp paper. The company has not provided the salary slips for any of the salaries till now. Also, the bond is dated 17th February, 2015. I went through the and looked up the company's registration detail. It was registered on 10th April, 2015. I am not familiar with any of the labour laws. But is the bond that I signed even valid, if the company was unregistered when I signed it? And about the security cheque, I am thinking of making a stop cheque request with the bank (SBI). Will I be charged for any illegal action? How serious can this matter get? Please, any kind of help or advice is welcome.