At final I reject acf_form() because I don’t know how can I use it with hidden fields.
I think ACF need the setting “Hidden in front-end: true/false” and the parameter acf_form() “input_init_values” => $init_values.
For example, how must I do with acf_form():
Question post about some item:
1) item_id (hidden for user in front-end)
2) title
3) message
Without acf_form() it will be:
<form action="<?php echo get_stylesheet_directory_uri() ?>/question-update.php" method="POST">
<input type="hidden" name="item_id" value="<?php echo get_the_ID() ?>" />
<input type="text" name="title" value="" />
<input type="textarea" name="message" value="" />
</form>
