I have done some link development in past week by sommenting on other do follow blogs and other stuff but those link backs are not showing google how long google takes to show backlinks?
Sometimes never, if you are using the "link:url" search query in Google. Your best bet is to use any number of backlink tools or Yahoo site explorer. In any case, it takes differing amounts of times for different sites, but as a rule of thumb, count on about two months.
mauik is right, it can take a while for some of the pages the links are one to be re-indexed within search engines. The more popular the page your link is on the faster it will show up... but some back end directory link in a bottom category could potentially take years to be re-spidered, where as a link here on DP can show up in the google index within minutes (though I'm unsure how quickly the link will count as a backlink). I've never heard that rule of thumb. I'll write it in my rule of thumb book
Are you using the link:website name command or, are you looking in your google webmaster tools? Using the link: command - some links may never show up. In google webmaster tools - on average around 3 weeks. I have seen my links show up in my google webmaster tools at as early as 2 weeks and as late as 2 months. I would say around 3 weeks on average, plus or minus a couple of days. Part of it depends on the crawl rate of the site and if the site has a site map generator. If the website owner has a site map generator installed, the pages will get indexed faster.
Yes i was using Lin: Domain method and also if backlink is not shown on this method does that mean it is not considered or is it that google does know the backlink and only doesn't display on this method?