There is no Hustle Castle offline app or apk mod available. If you want to play the game your going to need an internet connection to due so. Other website might claim to have an offline edition, but they would be wrong in saying so and probably are trying to get you to download an app that doesn’t work or is hacked.
Probably the main reason why you need an internet connection is so the developers can make sure people are not messing with the app. If they could then no money would be able to be made from timers set on things and the speeding up of them.
You might have noticed already, but any time you open a chest the game will connect to the game servers to give you and record the data. Many other action are kept online so that game features like raiding other players can take place. Since many battle are just fighting someone else’s stats while they are online and offline the information has to be stored somewhere so the game can work.
Once you have them games loaded there are a number of things that can be done without having the internet, but just about everything that matters will use it so your gonna have to have it for normal playing. It would be nice if more game had an offline option, but I guess they wouldn’t make as much money. Many of the good games for mobile tend to need an online connection which can put a damper on things when trying to play on the go.
Since they game is recorded and seems to be run from servers somewhere else is does have various features where things can be earned while offline like collecting resources.