Using Apple as an example:
www.apple.com < --- Main company site
www.iphone.com <--- Product
www.imac.com <-- Product
If each company product had its own domain name and a unique webpage or website containing an anchor link back to the main company site, would that increase the PageRank for the main company site?
If the main company site had a navigation bar with links to the different product domain sites, would that positively or negatively effect PageRank for either the company site or the product sites? (I believe this is referred to as cross-linking).
Lastly, would a 301 redirect from the product domain to a directory on the main company site (e.g.,
www.apple.com/iphone) negate the benefit of the backlink?