Am I on product or localhost? How to detect the environment?

I'm not sure what you mean. I think there are many ways of determining or checking if you are on a production or development environment. I would do this way I would check what $_SERVER['SERVER_NAME'] returns and if i decided that localhost is development environment and $_SERVER... returns 'localhost' is development f.e. localhost i could set the standard $config variable value into $config->development=true (after config is initialised or during initialisation with ("development" => ($_SERVER['SERVER_NAME'] =="localhost")?true:false) or something like this ) This in turn (i assume you register the config in the di variable as Phalcon tutorials show) could be used in your controller action this way (if you wanted) $this->config->development or you could use differnt settings for database for di. Some other users could give you some better tips.

for example, I want to use different connections for local developing, and for products. So I have to distinguish the two (and I dont want to always edit the settings when uploading)

If you set the config variable as i suggested (you don't need to but you then have the config variable accessible in controller, models, etc) you could do something like this

$di->set('db', function () use ($config) {

    if ($config->development===true) {

      if (strtolower($config->database->adapter)=="mysql") {

          return new DbAdapter(array(
              'adapter'     => $config->databasedev->adapter,
              'host' => $config->databasedev->host,
              'username' => $config->databasedev->username,
              'password' => $config->databasedev->password,
              'dbname' => $config->databasedev->dbname
          ));

      }    
    } else {
      if (strtolower($config->database->adapter)=="mysql") {

          return new DbAdapter(array(
              'adapter'     => $config->database->adapter,
              'host' => $config->database->host,
              'username' => $config->database->username,
              'password' => $config->database->password,
              'dbname' => $config->database->dbname
          ));

      }    
    }  
});

Your other services (like autoloader autoloading directories/classess, namespaces) could be easily switched in a similar way.

You could use the example by @OpenEX but nstead of settings a development property of config, do this:

$di->set('db', function () use ($config) use ($di) {
    if ($di->get('request')->getHttpHost()=='your.dev.host') {
        // dev
    } else {
        // prod
    }
}