Theme development

I am creating a drupal 8 theme. On that theme I have placed a field for uploading banner image.

Below is the $form field construction for banner_image field.

Hello everyone , this is my first post so if i posted in wrong section feel free to delete it. So my question is how i can make website layout if i have given wireframe ? (D8) :) Thanks.

How to add the term id (tid) as a CSS class on every taxonomy term field?

Example: field_tags
Multiple value. If I display it using the Link formatter, I have this result:

I'm trying to customize user login form in (/user/login) page and I want to use a hook_form_alter function to add some awesome style and placeholder to each of user login form fields and remove or hide:
"Enter your admin username" and "Enter the password that accompanies your username" description expressions under each of theme.
I added something like below code to my ThemeName.theme:

Hello Drupalers,

I like Drupal and its been nice to learn about and get stuck into. Unfortunately I've hit a road block.

Use Case:

The application needs a hierarchical custom menu (Already exists)
The menu needs to be shared as a block within different regions (Achieved)
What seems to be the hard parts
1, Render the menu differently in different regions structurally and visually (i.e. a different surrounding css class)
2, Show or hide different nodes in the hierarchy

I want to learn how to develop a Drupal 8 theme. Which theme (besides Stark) best accomplishes the task without being so bare as to make visible progress move at a glacial pace?