Welcome to the forum. Horned frogs are sexed based on size usually. Females tend to be somewhat larger than males. Males may have darker throats too. These differences can only be seen in near-adult frogs. Small frogs usually cannot be sexed. Breeding is usually accomplished by first conditioning them with a dry cool period of months, followed by placing them in a rain chamber along with a pool of water. Very few people ever succeed in breeding these frogs - it's not easy.

Your other questions, as ArchGrammarian has said, require us to know which species you are talking about.