Knowing our natural reading order is from top to bottom and from left to right, a situation increased even more if it's about filling out a form, what you are trying to do is something totally unnatural.
– what are the options we have in this situation? –
It's impossible to answer this without knowing the form content.
If on a guided trip, almost reaching the destination, the guide tells the passengers that they must return to the starting point, he/she will surely be forced to give an explanation, at the risk that they abandon the trip (form).
If there's no other option and the form needs to force the user to take trips from the bottom up to complete it, the only way to make them first understand it and then carry it out is by explaining why and giving visual cues.
Explaining the reason
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