Due to troubled developments of Sonic 2, many levels are cut from it. Further informations on these cut levels can be found on the Sonic Retro (where most of the infos on this page comes from and be licensed under its license).
Sand Shower Zone is one of those scrapped zones from Sonic 2.
No known actual development started for the level, only a mockup image (see above) was created for it.
Sand shower Zone in StH: The Lost Worlds.
The level would be served as the basis for the Desert Dazzle Zone from the 2011 Retro Engine remake of Sonic CD (which was also scrapped), and later for Mirage Saloon Zone from Sonic Mania.
A scrapped Jungle-themed level.
If you used debug to going up you will find some conveyor belts on the top of the level.
Although this level exists in the level select menu in Simon Wai Prototype, selecting it just brings you to an empty level. The layout of the level was reworked into Metropolis Zone Act 3, and the art was recycled into Sonic Spinball.
The original title, "Genocide City", was probably due to the Japanese team misunderstood the word when they're looking for a word that sounds dangerous, according to one of the graphic designers.
Bonus: Early Fan Interpretations of the level
This zone is supposed to be an area where Sonic would got his Super transformation after gaining all 7 Chaos Emeralds. The 2013 remake of Sonic 2 added back the zone and finished it (complete with a brand-new boss), but you have to enter it by (spoilers? although it's pretty well-known by sonic community today falling into the infamous spike pit in Mystic Cave Zone Act 2 instead).
The original Hidden Palace Zone is also present under the name "Proto Palace Zone" (but with some tweaks to make the level fully navigatable), but you have to use an unlock code on the Level Select. Or just enter the dev menu and it's lying in the "Bonus" section.
Sonic 2 2013 is supposed to have a fully-fledged boss attack level with its own theme, but Sonic Team disliked this idea.
To be continued...