How to display node/add/sometype form on another page?

Question

The whole problem is following:

Lets say we have Items, Items can have Bids, Items can have Questions and Question can have Answer.

When an Item is displayed

Answer 1

// Drupal 7    
// Embed node creation form on a custom page inside module.
module_load_include('inc', 'node', 'node.pages');
$form = node_add('node_machine_name'); 
return drupal_render($form);

Answer 2

Thomas's answer looks good to me: Formblocks and perhaps automatic nodetitles. I think you could expand on that with Nodereference URL Widget -- using nodereferences rather than comments, and letting that module do the work of keeping child-nodes connected to their parent.

Answer 3

I am reproducing the solution which worked for me on my case. it is available as an answer on Drupal.org and it may help others with the same problem I was experiencing.

The answer is available here: https://www.drupal.org/node/1336212#comment-6192404.

I am copying-pasting it below:

in your custom callback OR in a hook_form_alter, call either...

<?php
form_load_include($form_state, 'inc', 'node', 'node.pages');
?>

...OR...

<?php
form_load_include($form_state, 'inc', 'user', 'user.pages');
?>

...depending on whether the core Drupal form you're loading is a node form or a user form.