My drupal site has a .htaccess file on which I am redirecting the page without changing the URL, Its working fine on local server & other servers but when I upload the files & databases to pantheon server It will not redirect the page saying 404 not found. I placed .htaccess at the root of code folder, I tried placing it in server root folder, sites folder & themes folder but nothing works for me. Can any body know what is the correct placement of .htaccess in drupal site on pantheon? & why my .htaccess not working on pantheon?
Because Pantheon servers use Nginx, and they don't enable .htaccess support.
You should contact them directly to discuss your options.
You can, however, perform redirects using Drupal’s settings.php, please see:
https://pantheon.io/docs/articles/sites/code/redirect-incoming-requests/