The Pokemon Sun & Moon Special Demo was released worldwide on October 18, 2016, exactly one month prior to the release of the actual games. It was available for free download via the Nintendo 3DS eShop, needing at least 3,000 Blocks of free space in order to do so.
This Special Demo, similar to that of the Pokemon Omega Ruby & Alpha Sapphire Demo, allows a player to get a first glimpse and feel for the New region of Alola. There are many restrictions, however, mainly just how much a player can do and where they can go, but it still lets one experience the gameplay for the upcoming games.
The player, dubbed the automatic name of Sun, has just moved to The Alola Region in the Demo, and he is only allowed to roam one city and one Trial area. You will quickly meet the main character friend/rival, as well as the Professor of Alola and Team Skull, before you are able to explore. The city has no real value of substance, which means the player will most likely spend much of their Time in the Demo in the trial area accessible at the northwest corner of the city.
There are just two trials a player can participate in, as well as an additional mini battling challenge. The First Trial is done with the Professor in the cave area apart of the Trial area, where the Professor challenges you to take a few snapshot of wild Pokemon. It is apart of this challenge that a player will further meet and Battle Team Skull.
The second Trial is only accessible after defeating the first, one in which the player will have the challenge of catching as many Pokemon as possible. After the first main trial with the Professor is also when a player can partake in the mini Battle challenge in the trial area, where the player will battle three trainers for a prize.
Apart from these activities there is not much associated with the Special Demo. Primarily, players are only downloading and playing the Demo to obtain the coveted Ash-Greninja, the only known way of obtaining such Pokemon.