only removing index.php rule works on my NginX and CodeIgniter as rewrite. Why?

Question

Although I've spent 2 days reading on forums, I still can't get some Codeigniter rewrites working in Nginx. Here is the server configuration:

server { listen *:80; server_name artademy.com www.artademy.com; root /var/www/artademy.com/web; index index.html index.htm index.php index.cgi index.pl index.xhtml; if (!-e $request_filename) { rewrite ^/(.*)$ /index.php?/$1; } if (!-e $request_filename) { rewrite ^/(index.php\?)/(.*)$ /$1/mobile_app last; break; } error_log /var/log/ispconfig/httpd/artademy.com/error.log; access_log /var/log/ispconfig/httpd/artademy.com/access.log combined; ## Disable .htaccess and other hidden files location ~ /\. { deny all; access_log off; log_not_found off; } location = /favicon.ico { log_not_found off; access_log off; } location = /robots.txt { allow all; log_not_found off; access_log off; } location /stats { index index.html index.php; auth_basic "Members Only"; auth_basic_user_file /var/www/clients/client0/web3/.htpasswd_stats; } location ^~ /awstats-icon { alias /usr/share/awstats/icon; } location ~ \.php$ { try_files $uri =404; include /etc/nginx/fastcgi_params; fastcgi_pass 127.0.0.1:9012; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; fastcgi_param PATH_INFO $fastcgi_script_name; fastcgi_intercept_errors on; } } 

Codeigniter settings are: well for uri_protocol: REQUEST_URI;

What I noticed is that from this rule: rewrite ^/(.*)$ /index.php?/$1; it works, but if I write it like this: rewrite ^/(.*)$ /index.php?;. It might be a wild guess but it stops at the question mark.

Anyhow what I need are rules as these from .htaccess:

RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{QUERY_STRING} ^lang=([a-z]{2})$ RewriteRule ^([a-z]{2})$ index.php?/home_page?lang=$1 [L,QSA] RewriteRule ^([a-z]{2})$ index.php?/home_page?lang=$1 [L,QSA] #how_it_works RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^how-it-works/(en)$ index.php?/how_it_works?lang=en [L,QSA] #order_status RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^order-status/(en)$ index.php?/order_status?lang=en [L,QSA] 

Can anyone tell me what I'm doing wrong and show me a proper way for at least one rule? It would be more than helpful. Thank you in advance! ^^

PS: I made it work on apache by using Path_info for uri_protocol. If this info is of any help. I remember having kind of the same problem there too but switching to path_info made it all good.

PS.2: My .htaccess is working fine, that I am sure. For example I want to rewrite from artademy.com/how-it-worksES/es to arademy.com/index.php?/how_it_works?lang=es