quick question:

I understand the under the so-called cross chargebility rule, if one side of a couple is born in a nation that is current in visa bulletin, the other side can file 485 without waiting. But the question is: if the spouse whose birth place is not china or india, but already got green card, can the other party still benefit from this rule please?

I do not think so. Cross chargebility rule applies only to the I-485 applicant, not to the green card holder or green card holder's alien spouse.