Module development and code questions

Hello,

I recently started a gig where I will need to start the process of upgrading a Drupal 7 site to Drupal 8.  I have been looking in vain online for sample documentation or templates I can use to start documenting the entire site. 

Thanks!!!

Hi, I need help to create a module that uses Stripe Connect with Drupal 8.7, Drupal Commerce 2.14 and Commerce Stripe RC3 :

https://www.drupal.org/project/commerce

https://www.drupal.org/project/commerce_stripe

Currently there is no module with Drupal 8 to use Stripe Connect, it's a shame because Drupal Commerce makes it easy to set up a marketplace (a site with several merchants).

How can we remove or add HTTP header response values from drupal site for specific page?

Please help me on this!

in entity query,How to use another field as the conditional value?
like this:

        $entity_query=\Drupal::entityQuery("node", 'AND');
        $entity_query->condition("field_A", "field_B", '>');

But this doesn't work

because  in "condition($field, $value = NULL, $operator = NULL, $langcode = NULL)"

$value just is a scalar or array

I can think of solutions: :

   first step ：add query tag

   second step ： Implement query hooks

where we should write drupal_add_http_header()in drupal code, if we need to add header caching on home page only.
Do we need to create custom module?
or we can write in setting.php, using if (drupal_is_front_page()){ //code }

If I need to add response header for 1 hour, than is this code currect?
drupal_add_http_header('Cache-Control', 'public, max-age='3600');
and what should I use here public or private.

Please guide! Thanks!

I have created a rest export for a view. This view is for a specific content type lets say ContentA. The nodes of this content type, are in different languages, some in english and some in a regional language. 

I have added some fields in the rest export for this view and the GET requests shows them. But I want to display the language of the nodes as well. As I said that some nodes are in english and some are in another language. So how can I display the language of a node in the GET requests.

Thanks,