30 Amps won't "go through ring" unless you have 30 amps worth of load plugged into some sockets. I'm not sure what you are asking there.You should be able to test ring continuity at any socket on the ring.
Why is this a "bag of worms"
You have a circuit wired as a lollipop and you have established the terminals on the SO where it's fed from are large enough to take the 3 cables.
So exactly what is your issue? what are you trying to achieve? Are you wanting to make alterations to the circuit, or just doing a PIR and not sure how to report it?
I know Lollipop circuits have been discussed before, and nobody has found a reg specifically dis allowing them, but on the other hand neither has anybody found a reg that actually mentions them in any way.
My own personal take is the circuit is probably okay if the terminals can take the 3 cables without giving any a haircut, and it would only be an issue if the customer wanted new sockets, and the replacements had smaller terminals. Then you might need to find an alternative way of feeding the ring.