Tab focus from iframe to iframe of different inputs Javascript

I’m facing this issue for jumping between inputs using Tab key,
this iframe is loaded by third party payment gateway and each input is a different iframe in itself so whenever we try to press tab in any input it just does nothing (since inputs are inserted dynamically after page load), I have tried tabindex, jquery, javascript events, iframe related functions but nothing is working and whenever I try to access the input using this cmd “contentWindow.document” it gives cross origin frame error since js is loaded by third party.
please suggest me with some solution.

iframe Input boxes

I have tried tabindex, jquery, javascript events, iframe related functions but nothing is working and whenever I try to access the input using this cmd “contentWindow.document” it gives cross origin frame error since js is loaded by third party. Only “change”, “blur”, and “focus” events are available directly for inputs by external js.