<?php
// Link with title of first post in current post’s category
$first= get_boundary_post(true, '', true, 'category');
if (!empty($first)) { foreach ($first as $post) { ?>
<a href="<?php echo the_permalink($post->ID); ?>"><?php echo $post->post_title; ?></a>
<?php }} ?>
<?php
// Link with title of latest post in current post’s category
$latest= get_boundary_post(true, '', false, 'category');
if (!empty($latest)) { foreach ($latest as $post) { ?>
<a href="<?php echo the_permalink($post->ID); ?>"><?php echo $post->post_title; ?></a>
<?php }} ?>