Welcome to the Q&A Forum

Ok, the problem is your pages are all canonical to themselves, the canonical tag should point at the main page for the content, not to every page.  For your first example, all pages that get their content from http://www.spain-internship.com/en need to have canonical tags to that page, instead the copy page has this:

href="http://www.spain-internship.com/fi/etusivu/186-all-fi/home-page-fi" rel="canonical" />

it should have

href="http://www.spain-internship.com/fi/" rel="canonical" />

Meta descriptions do not effect your page optimization in the sense that a search engine is effected by it, but it will effect how often people click to your site as the meta description is the copy a person is shown. You should make your descriptions informative and truthful so that it accurately portrays what each page has to offer giving a potential visitor the best ability to judge what content will be on the page (and thereby lowering bounces/re-searches). This being said you should write custom meta descriptions, not just let it truncate content already on your page.  I would start with products that are relevant to the most used keywords and work backwards, if you dedicate yourself to doing at least 20 descriptions a week you will have all of your legacy products done in a year.

They are different things for used for different reasons. By using the robots to block any page behind a log in you will not have to worry about them trying to access that information at all. You should also have canonical tags pointing to themselves on all pages especially product pages and landing pages.

Dave,

Your best bet to keep these pages indexed but not have duplicate content issues is to add code that will place a canonical tag on search pages based on the original search query so that even when additional information was caused to load into the URL, such as your example, it would point back to the base page.  If you do not want these pages indexed at all you can do what Keszi said or block all search pages using your robots.txt.

I would not block your product pages or search pages but I agree with blocking your shopping cart funnel.

Google official explanation of canonical and some common mistakes Google sees when they are implemented.

https://support.google.com/webmasters/answer/139066?hl=en

http://googlewebmastercentral.blogspot.com/2013/04/5-common-mistakes-with-relcanonical.html

Like most social media buttons, any link involved is tagged nofollow.  There are really no SEO effects to adding a button like that onto a site.

It will not remove a page just because the link is gone. Your best bet would be to set up your back end to automaticly add a noindex meta tag into the of ads once they expire.

Example of tag

SEO is not all back links, content is king, traffic is important and on-page problems can drag you down.  Instead of worrying about rank and back links you should work on a content strategy, make sure what you control is optimized (fast page load, no huge errors, proper meta etc.) and work toward small, sustainable incremental gains.  If your competition is using bad tactics it will catch up with them, you can grow your position now and be primed to take over when Google catches them.

Yes, it needs to be a 301 redirect.  If your permanent homepage will be /en then you should 100% permanently redirect your old homepage, a 302 is just a temporary redirect you should only use it for temporary redirecting.

Its not hard to do a 301, here is some information for your devs.

https://support.google.com/webmasters/answer/93633?hl=en

You could, but I would not.  Using the canonical tag is telling the search engine that the pages are the same, such as using it on landing pages that may have additional dynamically generated additions to the URL to make sure that Google knows which is the original page.  For your site, each of your events is a separate thing, and how would you choose which event you made the main?  From an UX standpoint you could be driving people who searched for one event on a specific date to either the wrong date or wrong event all together, this would lead to unhappy visitors and a lower ranking of the page or your site as people pogo-ing from your site increased.

Pixel tags do not effect your SEO. The only thing that could cause a problem is if they are loading slowing and causing load time issues with your site, otherwise back end code for tracking does not have anything to do with how you are ranked in search.

Then the answer is no, do not worry about keyword/content optimizing pages that you do not want ranking.

The first question is why are you going to have many stores doing the same thing, is each one unique in some way? 
Without more information as to why you are doing it this way it is hard to help with the best way to handle it.

I worked on a similar problem, we created an interstitial page for a general product and then used canonical tags to point all of the e-commerce product pages back to the interstitial page.

Ideally you would want one page where you could just select different options, but depending on your technology that may not be possible.

If those pages are being created due to those being tag options you should try deleting the tag to see if it stops wordpress from generating the page.

You shouldn't need to look specifically for analysts with experience with publishers. In general any good analyst can comprehend the needs and uses of any digital activity from web to app as very few industries are so different that their web data acts different or needs specialists.

The question is not dynamic v. static, it should be what is most readable for your visitors.  If you can simplify your urls for visitors then you should as it makes the experience better, which in turn is what Google wants websites to do.

I think you are more spot on with your 2nd option, creating content worth linking to is the best way to get real, quality links.

It is best practice to use nofollow tags and your robots.txt to keep search engines out of not only e-commerce pages, but also any areas that require a log in (such as a customer profile page or shopping history).  You want to do this so that they do not accidentally index pages that will redirect users who aren't logged in or create a weird/negative experience for them.

Just because you rate well on Bing and not Google does not mean you are being penalized.  Bing uses a less sophisticated algorithm compared to Google so different tactics (older ones) can rank you higher on Bing.  Just keep doing the right thing with content creation and adding value to your site that people who use the word "sensaphone" in a search will find useful.

While it is odd that the code has the content multiple times for the responsive, Google is very good at "seeing" what is being displayed (which is why all of the old keyword stuffing tactics don't work) so from that standpoint you should be fine.