
I am sure it hasn't changed, and I cannot see why the bunny would have been rung if it was a cross.
What happens when you have rabbits is that you purchase the rings at the beginning of the year, and then you ring the young rabbits. Each breed has a different size ring, and as long as the Rabbit is typical of it's breed it is extremely rare for there to be a p[roblem with it.
Now when breeding rabbits there is no pedigree database kept. some breeders keep written records and give their rabbits names, or just identify them by ring number, but when you buy a rabit you don't normally get a pedigree, as it would be meaningless to anyone bt the breeder.
So you won't likely find out when the Rabbit was born, or even who his parents were, unless his breeder happened to make a note of it. The only thing you can maybe find out is who the ring with that number was sold to, but I doublt it as it is likely to be private info. Maybe the BRC would be willing to pass on a letter.