Info about the theme

Sequential does have a grid page template, but it’s not something built into the front page, like in Edin.

https://sequentialdemo.wordpress.com/page-templates/grid-page/

Also contact page is displaying differently in admin panel and in incognito window of the browser.

Could you please provide a link to your contact page so I can take a look and explain exactly what is not displaying as you’d like?

I don’t see a contact form in either of those screenshots – what you’re seeing is the comment form.

Could you explain what the issue is specifically? It’s a bit hard to tell since you don’t show the entire browser window in the logged-in version.

I might need to see this live to be able to troubleshoot further – let me know when it’s up on a remote server?

Underscores is different from Sequential since it’s a starter theme, and as you said, not intended to be used as a base for a child theme.

On the other hand, Sequential is a full theme, and making a child theme of it is the right way to ensure that you can still keep updating Sequential without losing your customizations.

So you’re definitely doing the right thing!

do you have any suggestions how to upload child theme to server?

I would recommend using an FTP tool for that:

http://codex.ww.wp.xz.cn/FTP_Clients

Good luck finishing up the site!

How can I show up breadcrumbs?

Sequential displays breadcrumbs on pages through the Jetpack plugin. If you activate it – no special module is needed – you should see something like this:

On the mobile phone footer is green like a color of header, dont know why?

That’s part of the theme’s design – you’ll see the same thing on the demo site at screen widths less than 1020px:

https://sequentialdemo.wordpress.com/

You can override in your child theme if you prefer to keep it dark grey. Give this a try:

@media screen and (max-width: 1020px) {
  .site .footer-navigation,
  .site .site-footer {
    background-color: #313131;
  }
}