When managing a popular ecommerce, coupon pages are a natural source of traffic. Those pages make some linkbuilding for you, although you don't submit coupons to them.

If you have other type of links apart from the coupon sites, I would not give too much importance to this issue. Just check if some of those sites could be seen as spammy to ask for a link removal.

That kind of behaviour is really strange. Are you always searching from the same computer, and always logged off -or at least always in the same Google Account? Seems like you are getting some kind of customized experience based on your geolocalization, browsing history, Google Account or something like that.

For checking your ranks, always use an external tool like MOZ.

As long as you use valid HTML, use proper tags for titles and every section, and don't make the HTML size grow too much, it won't damage your rankings.

There is a limit of redirections which Google and the browsers follow in chain: you cannot create a loop, or make non-sense continuous 301 redirections.

But there is not a limit on the number of pages you redirect: in any redesign, all your similar pages (for example, product pages), will create a redirection. 600 is not a big number of products for an ecommerce site, or a big number or posts for a blog... Don't worry.

Matt Cutts speaks exactly about your doubt here.

It is a technical issue with your ecommerce platform. Definitely it is not good to have that kind of different URLs.

Canonicals are helpful with pages where you cannot do anything but having two similar pages on your site, or when there are almost identical pages. But when dealing with such an important page on an Internet project like the product page on a ecommerce site, you should definitely take action and manage to have unique URLs for every product, not depending of the path the visitor follows to reach that page.

It will become difficult to measure conversion rates or any other KPI on Analytics, and also will become a problem in SEO, with so many different pages to link.

Hello.

Don't panic: people won't see those results. You probably saw it because you have Evernote Clipper in your PC. This is a function of the Web Clipper Chrome Extension preferences. You saw this format of SERP.

To avoid seeing these results on your Chrome view, uncheck the box next to "When enabled, searching the web on supported search engines will also be performed on your Evernote account."