function wpa_parse_query( $query ){
    if( ! is_admin() && ! $query->is_page() ) {
        wp_redirect( home_url() );
        exit;
    }
}
add_action( 'parse_query', 'wpa_parse_query' );

# Redirect useless pages
Options +FollowSymlinks
RewriteEngine on
RedirectMatch 301 ^/portfolio/.*$ /gallery/
RedirectMatch 301 ^/author/.*$ /
RedirectMatch 301 ^/category/.*$ /
RedirectMatch 301 ^/tag/.*$ /
RedirectMatch 301 ^/20.*$ /