nginx config

Need someone that has knowledge of NGINX, basically need 2 things 1- Check Browser user agent, if agent is for example chrome,mozilla or opera than proxy info from server1 so if a url is called as [login to view URL] and user agent is chrome it will be called from http://server1:81/xx/xx if user agent is something else then it will fetch from server2 http://server2/xx/xx 2- Need another proxy if url is called as [login to view URL] the whole yy folder will need to be fetched from server1 or 2 based on the user agent will provide server to test on that has nginx/php installed.