I don’t have a solution for reversing the order of flex fields.
You could possibly use a similar solution to https://support.advancedcustomfields.com/forums/topic/inverted-repeater/ by loading all of the flex field into an array and reversing, however, this would mean rewriting all of the code to use values from the array rather than using the normal ACF have_rows() and the_sub_field() functions.
There is a solution for making the collapsed fields easier to identify here https://www.advancedcustomfields.com/resources/acf-fields-flexible_content-layout_title/
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