Module

Step 1. Install Tomcat And Solr Server (atlest 5.4.1)

Step 2. Install Solr Search API On your drupal

#Drush# drush en search_api_solr -y

Step 3. Copy solr core files

Drupal 8 Devel module has an integrated switch user block.  This function allow you to switch users without logout/login (for the selected roles) and without entering user name and password. To activate a this block.

Features is a drupal contrib module enables the capture and management of features in Drupal, by providing a UI and API for taking different site building components from modules with exportables and bundling them together in a single feature module.

Drupal 8 Hook System

This system allow you to invalidate drupal cache using a 'tag'

Exapples:

You can't change the body of this block fron the user interface. But you can do that using a small custom module using hook_block_view_alter().

You can find any entity using Drupal 8 EntityQuery System.

Example:

1. in yourmodule.links.menu.yml

yourmodule.test:

  title: Test

  parent: system.admin_config_development

  route_name: yourmodule.test

Module Name = my_module

Content Type = my_new_content

Create content type

Put this two files into my_module/config/install/

This is a drupal 8 contrib module allow  you (developer) to find code examples.