Sergey Biryukov

Automatically includes a parent theme RTL stylesheet for a child theme if it doesn’t have its own <code>rtl.css</code> file.
Thanks to <a href="http://www.wp-tricks.co.il/" rel="nofollow ugc">Rami</a> for the idea.

Include Parent Theme RTL CSS

Allows to include a parent theme RTL stylesheet for a child theme.

Makoto

This plugin allows you to insert html code into <a href="https://wordpress.org/extend/themes/mystique" rel="ugc">Mystique theme</a> without the need to hand code the original theme files.
This plugin will enable you to insert html code in the header and footer area. 
This plugin also will enable you to insert code into above your post and after your post content.

Guan Mystique Theme Code Inserter

This plugin allows you to insert html code into Mystique theme without the need to hand code the original theme files.

Include Parent Theme RTL CSS vs Guan Mystique Theme Code Inserter