Use this code to sort your Dynamic field options by the order the entries were added.

add_filter('frm_data_sort', 'frm_my_data_sort', 21, 2);
function frm_my_data_sort( $options, $atts ) {
    if ( $atts['dynamic_field']['id'] == 100 ) { //change 100 to the ID of the Dynamic field
       ksort( $options );//sorts options by entry ID
    }
    return $options;
}

Use this code to remove duplicate values from a Dynamic field. Please note, this should not be used if you are using the Dynamic field to link entries. It is only recommended when using a Dynamic field in a search form.

add_filter('frm_data_sort', 'frm_remove_duplicates', 21, 2);
function frm_remove_duplicates( $options, $atts ) {
    if ( $atts['dynamic_field']['id'] == 100) {  //change 100 to the ID of the Dynamic field
	$options = array_unique( $options );
    }
    return $options;
}

Use this code to sort your Dynamic field options if there is conditional logic on the field.

add_filter('frm_data_sort', 'frm_data_sort_conditional', 30, 2);
function frm_data_sort_conditional($options, $args) {
    $target_field_id = 100; // Change 100 to the child field ID.
    if ( $target_field_id === (int) $args['dynamic_field']['id'] ) {
        ksort( $options );
    }
    return $options;
}