When implementing hreflang in the head section, do you call out the alternative and main language on every single page?So for example if I'm implementing Brazilian Portuguese where the main language of the site is English, for my English site it would place the following in the head section:<link rel=alternate href=http://example.com/about hreflang=en-US /><link rel=alternate href=http://example.com/about hreflang=en /><link rel=alternate href=http://example.com/pt-br/about hreflang=pt-br />Then for the Portuguese site it would be:<link rel=alternate href=http://example.com/pt-br/about hreflang=pt-br /><link rel=alternate href=http://example.com/pt-br/about hreflang=pt /><link rel=alternate href=http://example.com/about hreflang=en />
Implementing the hreflang tag in the head
seo;language;hreflang;translation
Yes that is how Google know it.But use only one line out of these two lines, <link rel=alternate href=http://example.com/about hreflang=en-US /><link rel=alternate href=http://example.com/about hreflang=en />because it is pointing to same URL. I can't say weather it is harmful or not for SEO but if Google have any testing tool for hreflang then it will trigger some error on that.  So If your webpage completely written in US English language then keep it first line otherwise choose second one. Same apply to Portuguese hreflang links. On this Google official article you can see one example about that.It's a good idea to provide a generic URL for geographically  unspecified users if you have several alternate URLs targeted at users  with the same language, but in different locales. For example, you may  have specific URLs for English speakers in Ireland (en-ie), Canada  (en-ca), and Australia (en-au), but want all other English speakers to  see your generic English (en) page, and everyone else to see the  homepage. In this case you should specify the generic English-language  (en) page for searchers in, say, the UK. You can annotate this cluster  of pages using a Sitemap file or using HTML link tags like this:<link rel=alternate href=http://example.com/en-ie hreflang=en-ie /><link rel=alternate href=http://example.com/en-ca hreflang=en-ca /><link rel=alternate href=http://example.com/en-au hreflang=en-au /><link rel=alternate href=http://example.com/en hreflang=en />