How to properly prepare CSS GRIDs?

Question

Python

Good day colleagues!
Please tell me if I understand the following features of CSS Grid correctly:
1. Set a background (background) to a grid cell (or a set of cells - you can't)
2. Suppose we have a grid grid with 12 columns and 20 rows. I want to name a certain set of rows/columns, suppose I want to name the cells of the first row: 1st column - "left", 12th (last) column - "right", intermediate 10 columns - "header". Accordingly, I will have to write 12 words ( cell names, for one line), since the construction that would do something like: or in relation to the element whose specified In other words, for example:
grid-template-areas: "left header[10] right";grid-template-areas: "left header(10) right"; , where the number of cells with the same name is indicated in brackets, does not currently exist.
display: grid;

<ul>
  <li>
    <a href="#">Ссылка</a>
  </li>
  <li>
    <a href="#">Ссылка</a>
  </li>
  <li>
    <a href="#">Ссылка</a>
  </li>
</ul>

If you specify UL 's display: grid; , then we can only distribute LI 's on the grid, but not the A 's nested in them, regardless of their positioning and other parameters.

Answer 1

1. Yes, you can't.
2. Also true. You have to write grid-template-areas: "left header ... header right";
3. Subgrids or display: contents; Already explained in the comment.