That's correct, mostly. He doesn't need the hat since the other two cartoons that are public now depict him with different (or no) headwear. All three are black & white tho. This is from his wikipedia article:

On January 1, 2024, the copyrights of the first three animated Mickey Mouse cartoons and their portrayal of Mickey Mouse expired, and they entered the public domain. They are the silent cartoons Plane Crazy and The Gallopin' Gaucho, and the sound cartoon Steamboat Willie. Newer versions of Mickey Mouse will remain copyright protected.

Although Mickey Mouse lapsed into the public domain in 2024, the character, like all major Disney characters, remains trademarked, which lasts in perpetuity as long as it continues to be used commercially by its owner. So, whether or not a particular Disney cartoon goes into the public domain, the characters themselves may not be used as trademarks without authorization.