anyone please tell me how to separate combined objects and bring into original state in obj mode.

Duplicate your original object so you have two at object level. Then dive into each one and create a Group node that represents only the portions of the internal mesh that you want to keep for that object. Follow up the group node with a Delete node to remove that portion.

you can as well use Extract shelf tool

Thank's guy's for your help, i am from maya platform that causing such troubles in houdini, need to learn help, hope you guy's will be there )