Here's a couple charts and descriptions you can use: http://www.sitepronews.com/pagerank.html http://www.seocompany.ca/pagerank/page-rank-calculation.html
in you must not do anythink to become pr 1 . but there is no limit for backlinks. it's allways better to have more backlinks
depends on the backlinks you have, you could get PR1 with as little as 1 link, or have many and remain 0.
If you're talking about the minimum; I think you don't need any links to get PR1 - just keep it up for some time (about 1 year) and Big G will bestow PR1 on your site.
I have a three year old domain with five backlinks. I did SQUAT with it until I checked the PR on it about two weeks ago: it was magically a PR2. But that doesn't answer the question for a new site. Consider this: toolbar PR is updated every season basically. So you'll have to wait months maybe, anyway. Also, it depends on your site's niche. Also, it depends on WHO is linking to you. Basically, this is like black magic sometimes - it's all mysterious and unknown. So what to do? Get as many backlinks as you can from relevant sites. That goes for anyone.
When i get the back link from a web site,I consider the type of the site.I know the page rank method.But i need to know is "How long it will be taken for a new site"?.Just give me about your experience. Regards