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In my opinion and dealings they have. One thing I have noticed they do not frown so hard upon is redirecting the same word, different extension to the same site. Like site.com, site.co.uk, site.com.au Google is on to the tricks that your client is using, if the domains are not getting many direct accesses, then the 301 redirect will end up dying after a couple of weeks or a couple of months and be useless. Its a spammy and costly suggestion, but I know how clients that are set in their ways are. I would recommend to them to maybe set up variations of the same site at the different addresses. Different images, different content, different everything. Maybe have the same logo, but have the contact forms feeding into the same email address. I think more than likely you have been put into a tough situation by a not so good seo company that the client had before.

No, the page authority is earned by the links it gets from other sources. If it is a guest post it is probably a new page, therefore it has no authority yet, but it will earn it over time (the most links it gets the better (shares, etc)).