How do I edit the multisite home page, and edit default page templates?

In my multisite network, my network admin page shows I have 1 site and 1 user.

1) I cannot get into the network home page (site1) to edit content.

When I am in the site admin dashboard for site1, I only see 3 pages listed I can edit. I cannot see a root or / representing the home page.

(I managed to edit the home page before, and recall getting rid of an extra comment area at the bottom of the page. Maybe this created a new template somehow, but one I cannot see properly listed in the page template pull down menus).

Visiting the website while logged in, when I click on pages I see the "Edit Page" button on the admin bar at the top. When I go back to the home page/index, the "Edit Page" button disappears.

2) How can I edit the "page" default template of gridmarket, or any of the other default pages such as contact, etc. And how do I make sure these changes do not get overwritten after a theme update?

I would like to create a default "shop" page template I can use throughout the network of shops.

Thanks.