Domains age is also a point since spider has his records on older domains and sub pages. But ofcourse it's a must to still work on it. Websites need to be updated in order to be crawled.
There's no one single criterion that can determine a site's pr. A lot of multiple and overlapping factors go into its calculation...
Old aged domain with more and quality backlinks and with higher page rank is always better to get into top of search engine
there are a lot of factors which affect raking one of which is domain age also, it gets preference over newly established domains
no! age isn't important. the deal for good ranking: content (content is the king) and incoming links. that's (almost) all for the biz!