Parody is Fair Use and was thus allowed even before the copyright expired. What's new is being able to use Steamboat Willie in works that are not parody.
The original short is called "Mickey Mouse in 'Steamboat Willie'", so yes, this is Mickey Mouse by name as well. LegaleEagle has a video further discussing the details, TLDR a lot of this is uncharted water, and you may or may not get away with using a modern version as well
I don't see why he'd have to wear the hat it's not like it's part of his head why can't he take off clothes or wear different clothes also as for the gloves https://youtu.be/BBgghnQF6E4 look at the walt disney presents and the the end slide he's wearing the gloves he also has the modern eyes rather than the plain black circles maybe they could argue over red trousers and they could absolutely argue over the name but the gloves I don't think so