Google and other major search engine does not count multiple links from one page, only the first one counts. Is it true? For example I am making 3-6 backlinks for my site from 1 blog commenting. Would my site get SEO value for all backlinks or only for one backlinks? Can Google count backlinks as a human? How much backlinks are worthily from 1 blog comment or forum comment?
If you are using the same URL in your backlinks, the URL is only counted once. You would however benefit if the anchor text for each link included different targeted keyword phrases. If you each backlink points to a different resource (web page), each backlink would count as one. So if you have 5 links in a post to 5 different resources, it counts as 5 backlinks. Also keep in mind...the more outgoing links that appear on a page, the less weight each link will carry.
^ correct. if you want to rank for green apples, it would be best to say have say three links, with the following types of anchors: "green apples", "best green apples" "low cost green apples". Hope that helps!
Both of them could be only "supplement" link but not a main link you could rely on. You can use this type of link in low to none competitive keywords but not for medium to high competitive keywords. Google does not give much weight in 100 links form one domain compared to 1 link from 100 domains. However, it does still give values by the root domain authority power, DP and many powerhouse forums are a good example for this case. If you have checked and observed links via Google Webmaster Tools you would see your link in DP forums counted on "each" and "every single" thread you have had participated. Even saying this, just a numbers and quantity but not quality anyway.