Two questions on the use of the canonical tag in the page head crossing multiple URLs and sites. Here's the problem. We lost badly on a Google update at the end of September last year on an old established website, a dozen years plus. I'm tending towards Google perceiving a duplicate content problem.
First question: It's a shopping cart site on shared hosting with a www oursitename dot com URL. We also use the shared ssl certificate which has a https oursitename dot hostingname dot com URL. This creates an alias URL duplicate of our site in both secure and non-secure URLs. So is it OK to have a canonical tag in the page head pointing from the alias url towards the equivalent page on the www oursitename dot com url?
Second question: We have an even older website which has country specific url, i.e. dot co dot countrycode, aimed at our home non-US base. It contains pretty much a duplicate of what's on the dot com. The reason why they were separate websites is complicated but has nothing to do with seo, either black or white. For these dozen or so years Google seems to have been happy with this although we always push the dot com site to be the lead site with search engines by supplying sitemaps, feeds and such. Anyway, would it be acceptable practice, or acceptable to Google, to put a canonical link in the country specific website to the dot com one?
The shame is we lost 80% of our Google traffic last September, but prior to this Google seemed to be happy to use us almost as an authority site. Now we have lost all our long-tail searches to websites that really don't serve the niche we supply. These are the searches that make our money.