AdSense has nothing to do with Google PR. In fact, traffic or revenue also does not have any direct relation with Page Rank. Page Rank is calculated based on the number and quality of links to your site but that is not always a good indication of the quality or popularity of your site. If you get a single link from a PR 6 website to you blog, your blog may get PR 4 or PR 5 with almost no traffic. I personally have PR 3 site with over 25K page views per day and have multiple PR 4 sites with less than 10% of that traffic.
Typically, Google require Indian publishers to have functioning blog for 6 months but they are not really very strict on that. I have seen many publishers getting approval before that. If your blog has lot of good quality and unique posts, you may apply.