How do I change the color of selected page on blog menu

Hi All, I'm new to this. I'm trying to wrap my head around the categories of Blog posts. Example: If I want a blog post to only appear on a page and nowhere else, how do I do this? It seems that when you choose a layout for your blog posts, then choose a category, it ultimately disregards the assigned category and displays all blog posts on the page. Example: I have a page called "Society." I want all the "Society" category blog posts to appear on that page and none of the other categories. I can't seem to get it to do that. I think I'm misunderstanding the purpose of categories. What am I doing wrong? Thank you!

I am unsure if this has been asked, if it has I cannot find the post/answer. When attempting to login to my site via a social (facebook/google) it says "Access denied by site owner." Why does it say that and how do I fix it to allow for social logins?

I've seen a number requests for customizing blog headline and detail to allow for copy, however no options. Is there a way that we can go into the code ourselves and change the parameters to allow this? Simple things like changing text size, kerning, and line spacing. Also we should be able to place customized fields. I'm not seeing simple, normal HTML code editing & mods available like in Drupal, Hubspot, etc.