css: dir="rtl" VS style="direction:rtl"

Question 1

As you can't modify the HTML, a really really hacky selector would be:

div[style*="direction:rtl"] {
    ...
}

JSFiddle demo.

Note that I'm using style*= as opposed to just style= as this will also match elements which have more than just direction:rtl declared within the element's style property.

For extra strength in the selector, you could also use [style*="direction: rtl"] to handle style attributes which separate the values from the properties with a space:

[style*="direction:rtl"], [style*="direction: rtl"] { ... }

Alternatively in this case you could just match on a style attribute which contains "rtl", as I'm pretty sure this combination of characters isn't used in any other property (ignoring external resources like background image file names):

[style*="rtl"] { ... }

Updated JSFiddle demo.

Question 2

Use dir="auto" on forms and inserted text in order to automatically detect the direction of content supplied at run-time

<div dir="auto">Hello, world!</div>
<br/>
<div dir="auto">لا إله إلا الله محمد رسول الله</div>
<br/>
<input type="text" dir="auto" value="Hello, world!" > 
<br/><br/>
<input type="text" dir="auto" value="لا إله إلا الله محمد رسول الله" >

JSFIDDLE Demo https://jsfiddle.net/80k0drsf/

Question 3

just add class "rtl" to html tag

<html dir="rtl" class="rtl">
 <head>
   <style>
      html[class*="rtl"] body {
         background-color:blue;
      }
      html[class*="rtl"] div{
         background-color:green;
      }
   </style>
 </haed>

 <body>

 <div>
 </div>

 </body>
</html>