I had already created the network and modified the IP address BEFORE clicking the blue question mark button, which seemed to prevent me from editing it. After a restore of the config and clicking the blue ‘?’ first, I could do it fine. Thought I’d post this back as advice.
After searching the internet I read on a website called routersecurity.org that ‘Inter VLAN Routing’ is enough…
Any help appreciated on this certificate question, for completeness I’d like to create my own Certificate…