by law you can not force your company to give NOC, unless it stated in your contract and agreed by both parties in written format.
you can make complaint against non receipt of your salary for the past 5 months. first try to get your arrear salary first, then you negotiate with your boss for NOC.

If you get a good job then you can ask your boss to give NOC and tell him that he can compensate NOC against your final settlement, this what most people do and this is the final and least possibilities for the same.