1. Admin -> Forum -> Posts and Topics. Set "Courtesy Edit Wait Time" to 0.
2. Yes, but not without editing the code.
Sources/Post.php
Find
if (time() - $row['poster_time'] > $modSettings['edit_wait_time'] || $user_info['id'] != $row['id_member'])
Replace
if ((time() - $row['poster_time'] > $modSettings['edit_wait_time'] || $user_info['id'] != $row['id_member']) && !($user_info['is_admin'] || $user_info['is_mod']))
Find
if (time() - $row['poster_time'] > $modSettings['edit_wait_time'] || $user_info['id'] != $row['id_member'])
Replace
if ((time() - $row['poster_time'] > $modSettings['edit_wait_time'] || $user_info['id'] != $row['id_member']) && !($user_info['is_admin'] || $user_info['is_mod']))
The line numbers are based on a default installation and may be different if you have any mods installed that modify Post.php.