如果父母现已在美国,探亲签证入关,是否可以在美提交在广州转身份的申请?
-Yes.
如果可以的话,需要遵守入关后90天再提交申请的rule?
-Not need.
如果转身份的申请被拒,现有探亲签证还是否有效?
-Yes, but they may have trouble to enter US using B2 visa due to immigrant intent. Of ocurse, the possibility of their immigrant visa denial is very very small, so you may just ingore it.