What is Fortnite Unblocked version and where to get it? 

First of all, you need to figure out what a locked game is. Usually, access to some resources (sites, blogs, games and social) is blocked by IP-address. These can be schools, colleges, or government agencies. So if you try to play Fortnite at school, you may have difficulty.
Fortnite is unblocked and there is no need to download any additional version. 
But if you don't have access to the site, you can use VPN services that replace your IP address.