I am trying to add video on my mobile site homepage by adding code in templates/mobile_iphone/index.php

I simply added youtube code and it worked. But I only want that video on homepage not all pages.

For that I created a new module position in templates/mobile_iphone/index.php (where i had my youtube video) adding code
<jdoc:include type="modules" name="moduleposition" />
and tried to add youtube code from admin panel using custom code module. I assigned that module to my mobile site home page giving position as i gave in my index.php file.
It didn't worked.

Am i missing something?

First of all check that custom module contains your code, because of visual editors (like TinyMCE) strips iframes from content. Then try to assign module to all pages to check that it's correctly displayed in this case. And if you changes homepage for mobile browser (using corresponding MJ setting), check that the module is assigned to mobile homepage.