To get all 3 god mode fury frenzy and arena brawl you must first complete the game and 2nd have a free game slot to be able to do god mode and fury frenzy.

God mode
In god mode you can get hit by any thing and not get any damage done to you

Fury frenzy
In fury frenzy you will get unlimited speical power like the fir but you must beat the dragons before you can use all of them

Arena brawl
In the game there is a part where you go into a gladiators ring areana brawl is the same.