Did you tried to edit your theme or plugin in wordpress admin plugin editor page. On that case , better if you can remove edited theme / plugin from wp-content folder and re upload via FTP.
1 . Re-save your site permalink set from /wp-admin/options-permalink.php
page, that will flush rewrite rules.
2. If you are using any plugin related to gallery
, try deactivate it.
3. If you are using any plugin that restructure / generate permalink rewrite rules try deactivate those.
Looks like the theme you are using that doesn’t support sticky post.
I think you have to, if your issue is something which only can be fixed using admin access. In that case, you should always backup your site before giving someone access. After getting work done, change your admin password immediately. That will keep you safe side.