How to work with relocation issues during phd? I have worked for 3years as phd researcher at universityin country A. Because of some critical family relocation issues, i had to move to my family in country B. My maximum research work is done but due to travel restrictions in country B, i can not go back to country A for longer period of time . What are thr possible options available?
That needs to be worked out with your advisor and the university. The worst outcome is that you have to abandon. But working remotely may be possible in many fields. You would need to establish a regular communication regimen with your professor, of course, and possibly also find local resources (Library, computing...) to enable you to continue. But with the research largely done it may be a simpler matter than you think. 

Organizing a defense of the dissertation will be a challenge, but, with some expense, it might be arranged remotely. The university likely has AV facilities on its end to enable it. 

It might not be easy, and it might cost you a bit of time, but, subject to restrictions imposed by the field (lab work, ...) it should be possible. But it will put some burden on your professor and the committee that they will need to agree to.