The audit is for all pages and not only one. What happens in the majority of the cases is that pages / posts have similarities so you can group them together. For example the pages of a website may be ok but the blog post pages may be missing titles. It’s a lot of work especially for a 500 pages website but you can start from the most important pages first and work your way to the rest
Links to your site are extremely valuable – When another website links to yours, search engines consider that an indicator that your site contains valuable content. Not so long ago, getting dozens of links from low-quality sites was all it took to boost your ranking. Today, the value of a link to your site depends on the quality of the site that linked to you. Just a few links to your business from high-traffic sites will do wonders for your ranking!
Google recommends that all websites use https:// when possible. The hostname is where your website is hosted, commonly using the same domain name that you'd use for email. Google differentiates between the "www" and "non-www" version (for example, "www.example.com" or just "example.com"). When adding your website to Search Console, we recommend adding both http:// and https:// versions, as well as the "www" and "non-www" versions.
Search engine optimization is a method for sustainably influences search engine rankings. Google and other search engines calculate their search results for keywords using highly complex algorithms. The individual ranking factors and their weighting within the ranking calculation are well-guarded intellectual property that belongs to the search engines and is not publicly disclosed.