wc_get_product in a none woocommerce page

If I got it right – I can only use wc_get_product if the current page
is using the WooCommerce plugin. Since it’s a post page it does not
includes the WooCommerce plugin and hence I can’t use the
wc_get_product.

(Please currect me if I’m wrong – I’m here to learn 😀 )

You are wrong :D.

There’s a fundamental misunderstanding about how plugins work here. Pages don’t ‘include’ plugins. Plugins are installed at the site level, so what’s important is whether or not the plugin is installed on the site.

So there’s no reason you couldn’t use wc_get_product() wherever you wanted, as long as WooCommerce is installed. You can pass it an ID to wc_get_product() to get the product details on any page, like this:

$product = wc_get_product( 12 ); // Assuming the ID is 12.
echo $product->get_sku();

EDIT: Based on the edit to the question, the problem becomes obvious: The problem is that your get_product_info.php file is just a PHP file sitting on its own. It’s not even loading WordPress, let alone WooCommerce. Please refer to the documentation for how to do AJAX in WordPress.