Do I have to use Storekit to process asset bundles? So lets say I want (at runtime) for the player to permanently download media to their device for the game, will asset bundles work for this without using Storekit?
No, its not needed to use StoreKit
The StoreKit API actually wouldn’t even offer that to you.
but you must use StoreKit if you want to sell anything, no other payment gateways are tolerated other than the appstore
So will the asset bundle store the downloaded package permanently?
AssetBundles are packages that contain data. They do not store anything.
Your application would need to store it (System.IO.File.WriteAllBytes with WWW.bytes) and can do that so you can later on request it from the applications documents directory through WWW