Can I install android 5 before version of "V20b April 7,2014"

I bought my phone almost a year ago even though I have been getting a message about an upgrade for a long time I haven't installed it. Now I want to upgrade my android . I notices its version V20b April 7,2014. So what should I do ? Is there never version of android I can install directly or I have to install the next version first than the version which has already installed.My current version is 4.2.2