Hey @SE1217707,
Thanks for updating in!
1.) You are about to modify the theme’s built-in header designs. What you are trying to accomplish requires custom coding which is beyond the scope of our support under our Support Policy. If you are unfamiliar with code and resolving potential conflicts, you may select our One service for further assistance. meanwhile, you might want to check out this old thread:
Again, we highly recommend that you upgrade your X theme to Pro theme instead to be able to utilize the Header Builder and the Footer Builder which will allow you to create custom header/footers for the entire site or select pages only.
If you just want to insert your Logo Image on top of your header, you can surely do that in Cornerstone > Theme Options > Headers > Logo Image.
2.) Assuming that you have added the logo image in the Theme Options, it should be displayed through out the entire site.
3.) You can do that in Cornerstone > Theme Options > Stack > Topbar Background because it will also change the color of the Footer background.
Kindly let us know if this works out for you.