apache - apache2 is throwing internal server error 500 after AllowOverride All, localhost -

i new in configuring server. now, have configure localhost lamp , opencart framework. still throwing internal server error 500.

even have tried following things

sudo a2enmode rewrite apache2ctl configtest // syantax apache2ctl -t // syntax 

/etc/apache2/sites-available/000-default.conf file

    servername localhost      serveradmin webmaster@localhost     documentroot /var/www/     <directory "/var/www/">             options indexes followsymlinks multiviews             allowoverride             order allow,deny             allow     </directory> 

/etc/apache2/apache2.conf

<directory />     options followsymlinks     allowoverride none     require denied </directory>  <directory /usr/share>     allowoverride none     require granted </directory>  <directory /var/www/>     options indexes followsymlinks     allowoverride     require granted </directory> 

/var/www/opencart/.htaccess

options +followsymlinks header add access-control-allow-origin "*" rewriteengine on rewritebase /ot rewritecond $1 !^(robots\.txt) 

after checking logs, have found invalid parameters headers. therfore have this:

sudo a2enmode headers