Drupal 8.x

I am a product manager for the company I work for, which has been in business for nearly 20 years. They have a process which imports XML files and then performs extensive calculations to generate specific documentation. We are now planning to build a "portal" in which we will introduce a variety of new web-centric products and communication between individuals and companies. I am certain that most of the portal functions would fit well into the Drupal model. But I'm unsure about some the most critical points.

I have a block view generating a list of fields. Now i would like to style that list with twig.

What I can do is to add a .twig file like
block--views-block--blockname-block-1.html.twig
But how to iterate through the fields in {{ content }} to style them?

How to install drupal for our new started website RMOS Consultancy ?

I downloaded Devel yesterday and I am using Drupal 8 beta 15.
I am a complete newbie. I am not sure what to do to fix this issue?

This is the error I get:

Fatal error: Call to undefined method Drupal\field\Entity\FieldConfig::getDefaultValueLiteral() in C:\PHP\drupalbeta15\modules\devel\devel_generate\src\Plugin\DevelGenerate\ContentDevelGenerate.php on line 169

I posted my question in this link as well:

https://www.drupal.org/node/2567757#comment-10390589

I'm using Drupal 8 and I'm trying to create a datepicker in a form and get the value of the datepicker. Seems like this should be simple. However, the value does not change on form submit. Here's sample code:

$form['date'] = array(
'#type' => 'date',
'#prefix' => '

',
);

in validateForm():

Hopefully I'm asking the right question here, but I may have some wrong assumptions so apologies in advance. NOTE: Feel free to link to documents if there are any that explain this distinction!

I've been reading up on D8 and I was wondering if someone could explain the distinction between services and plugins? For instance, BreadcrumbManager is a core service; BlockBase is a plugin. In both cases it looks like you define the class, but with differences: