The value of any website is based on what it is worth to a particular buyer. Some people may place a value on the age of a website (or of a URL) but often age is only a factor if it means more backlinks, older links, more indexed pages, etc... If an old website had two indexed pages and no backlinks, I don't think that many buyers would put a significant premium on the value simply because the site was aged.
Likely YES. Another urban legend is that you domain expiration date also affects your website rank (or worth). The far - the better. Soon expiration may be considered by Google like "non serious business", i.e. scam or spam site.
Personally I don't think so, However, Google seems to love older websites. You make more money selling if you get loads of traffic and cash.
Age does matter when it comes to the fact that all this while the site has developed good content and backlinks... otherwise i personally dont think it matters much
There is the complex of measures which are very important. So that is quite difficult and useless to state something is useful and something is not