Unfortunately even recent versions of Android have some incompatibilites with OpenVPN.
When I tried again with Lollipop last month, the VPN's preferred DNS was not being set on the phone despite being sent from the VPN server, hence DNS lookups were leaking to whatever DNS server had been set before establishing the VPN. Quite a nasty gotcha. Workaround is to run a script to set the DNS, but that requires root privs which 'normal' users won't have.
When I tried again with Lollipop last month, the VPN's preferred DNS was not being set on the phone despite being sent from the VPN server, hence DNS lookups were leaking to whatever DNS server had been set before establishing the VPN. Quite a nasty gotcha. Workaround is to run a script to set the DNS, but that requires root privs which 'normal' users won't have.