Well of course it's an online game since i suspect that most parts of it (gold,gems, etc.) Is probably server sided.
But sometimes there are things that the expert hackers/cheaters of iosgods can figure out like editing the rewards that you get after finishing a stage/chapter.
Just trying out my luck here, hoping some of em takes a look at this request ^^
But as far as I tried for now 4 things worked for me :
-Edit time in Proving Grounds
-Edit Coins in War Guardian
-Edit Gold WHILE you are playing a Bonus stage (so its just bonus stage gold)
-In an alliance Team Raid you can edit the time also. So you could with the right team theoretically fight the boss till you get tired of it. But the other members will be able to view your reached Damage Rank So it's not that wise to abuse it especially at low lvl.
PS: If by "online game" you ment an MMORPG than no it isn't