Short answers, pulled from the story.
Nickelodeon officially launched on the 1st of April 1979 as the first cable channel for children. The channel began as a test broadcast on the 1st of December 1977 as part of the QUBE system in Columbus, Ohio. It was initially distributed to Warner Cable systems via satellite on the RCA Satcom-1 transponder.
The name Nickelodeon comes from the nickelodeons, which were the first five-cent movie theaters that operated in the United States during the early 20th century. These venues offered a cheap escape for working-class families and served as the precursors to modern movie theaters. The concept involved paying a nickel to watch a short film.
Advertising was introduced to Nickelodeon in January 1984 after the network had remained commercial-free since its launch. The network gained a rebranding in programming and image that same year. This change led to the network and its sister networks MTV and VH1 being sold to Viacom in 1985.
The first major use of green slime occurred on the game show Double Dare which premiered in 1986. The host Marc Summers would often douse contestants in the green goo as a penalty for losing a round. The slime was a mix of water, food coloring, and a thickening agent.
Nickelodeon Universe at the Mall of America opened as the first indoor Nickelodeon theme park in the United States before being re-themed to Nickelodeon in 2007. The park was previously themed as Camp Snoopy and The Park at MoA. It contains a variety of Nickelodeon-themed rides including SpongeBob SquarePants: Rock Bottom Plunge.
Nickelodeon and Triple Five Group opened a second Nickelodeon Universe theme park in the American Dream Meadowlands complex on the 25th of October 2019. Upon opening it became the largest indoor theme park in the western hemisphere. This title was previously held by the Mall of America's Nickelodeon Universe from 2008 to 2019.