Blackface was a thing that was invented by white people to make fun of black people. It exists for the express purpose of creating characatures of black people.
No. In some contexts, it has been used for that purpose. But blackface is also part of the very ancient folk customs and traditions of the British Isles, and in that context has nothing to do with black people. In some regions it would be entirely appropriate to wear blackface for Hallowe'en. See 'guising'.