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.
Yes indeed, as Buffy says. Talk to your professor. And be as kind and polite and cooperative as you can. Your prof is motivated to help you finish your degree. It looks bad for your prof if you don't finish.
Most universities are at least a little understanding about family problems. Your prof may advise that you ask your department or your school faculty for some assistance and consideration. Most especially, they will probably be open to letting you do some of the requirements through things like email and video linkup and such. And they may allow you some extra time for your degree.
Especially since you have already done 3 years. It probably means your residency requirement is complete.
I went through a lesser version of this in my PhD. My prof got a tenure track position at a different university in a different province. By that time all I needed was to finish my thesis. So I did that while physically located at the other university, but staying a student where I started. The university was somewhat understanding.