I'm asking this out of curiosity as I'm sure it was mentioned at requirements of a dog show judge seminar.
Am I right in thinking if you don't judge CC's (for example on C/B List) you can't judge a group at a open show?
Also theres restrictions on how many classes and breeds you can judge?

A judge has to be approved to award CCs (and previously done so) to be able to judge Variety Classes, Groups & BIS at an Open Show.
The number of classes you are allowed to judge depends on your position on the breed clubs list & the breeds Studbook band.