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No, that's not true.

Think SASS or SCSS are processed at server-side, and get a normal CSS stylesheet to the client.

SASS or SCSS can help you to manage your CSS files and classes, but you need to pre-process them to generate the final CSS sended to the client. If the final product doesn't change, seo will not change too.

There's no reason to leave index.php in different URIs, simply i have defined all links with their name, for example, for a root page from a section, the uri are defined as /project/index.php, not /project/ only.

I can clear them, or leave it. There isn't the problem. My problem are the moz stats returning non-linked inexistent addresses, and i doesn't know why.

Also, i've detected a failure who makes moz to find duplicated pages (A erroneous link with only a parameter) and i've corrected already. But i cannot find the reason for the inexistent pages.

Any javascript effor is invalid for SEO. Google doesn't read them.

You can try to make it on PHP, it's not complex, search your an replace with meta desc=$var and <title>$var2 (and, also, </head>). Then you can set the meta desc and page title with a variable in your code, and then this effor effectively have SEO value, because when the search engine fetch the page they have title and desc.</p> <p>Maybe this is more work than JS form, but also it's better for SEO and web itself (The JS run takes time on client side).</p></title>

You're viewing this information probably because you doesn't have defined your lang in the html tag.

And, also, you can change the lang of the page reading the lang of the client. But this doesn't have any effect on SEO.

I think, if you want to be crawled for all the world, you need to get another domain (Neutral one, as .com for example), and redirect all visits who doesn't have user-lang en-uk to these domain. You will mantain your actual score and start to make a new one too.

Google normally gives some priority on local market to local domains.