You can breed them as soon as they reach their senior weight. Most breeders wait until they're about 6-7 months old for their first breeding. If you breed them for their first time when they're older it can be harder for them to get pregnant as they have more fat built up; which can lead to smaller litters and more problems giving birth. It's ideal to breed them before their one year of age; after two years of age if they haven't had their first litter I personally wouldn't consider purchasing a rabbit for breeding.
If you have any questions about showing feel free to ask me. Mini lops are a fun breed; because they come in so many colors, and all solid colors show together so a single class can look like a rainbow. They pose with their head down; a lot influence is given on bone and body; they want a large, wide head, thick legs, and a compact, deep body. The ears are supposed to thick, and held wide open at the wide, and they fall in a horseshoe shape, sticking close to the sides of the face. Males usually have better heads, while females usually have more depth from what I see. Unfortunately, some of the nicest mini lops, especially does, often fall JUST over the weight limit of 6.5 lbs so that's something you have to watch.