Southperry & Nexon Collaborative Event

Its the reason behind it I'm after.

Having never run these websites before, I thought the way it works would be when form loads (as back button pressed), the form gets reloaded, hence losing its state as the answers were randomized; but if the form never reloaded, then the questions must have gotten reshuffled at the client side.

The OP of this thread says the following;
"If you do not answer and come back on the same day you will have the same questions. Answer order will change each time the page reloads. Answers can not be changed once submitted."

The average browser back button returns to a locally cached copy of the page, how the browser remembers it being. We have no control over yours exhibiting the unusual behavior of actually going to the address it was previously at and reloading the page instead. In most browsers one would have to have gone out of their way to explicitly force that behavior.

Since in that circumstance you would've had to manually redo all the checks on the page before you could resubmit it you shouldn't have re-answered based on the ordinal position of your answers, and I guarantee your browser did not retain the ordinal position of each answer if it reloaded the page, if it retained anything whatsoever from a previously loaded form it would've retained the selected values themselves, not their position on the screen. That's why a refresh of an attempted form submission in most browsers resubmits the exact same form.