3 advancements to Multimedia created by Walt Disney.

Explanation:

The first cartoons with synchronized sound:  The first of such cartoons is Steamboat Willie  produced in the year 1928 changed multimedia entertainment because there was synchronized sound with visuals for the first time.

The first full-length animated feature film was Snow White and the Seven Dwarfs , a 1937 production. And more recently, the Walt Disney Theme park.

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