Let's say one of the person, in this state, describe his/her earlier soul incarnation as being in some other country which has a different first natural language. Can we talk to that person, in this state, in his/her old country first natural language, which he/she have never learned before?

Science is not just about performing some experiment and reaching some conclusions, but it is also about trying to figure out the implication of those conclusions and experimenting with those implications.