Hi there. New on this site, but I've been playing the iPhone game for some time now and I've got answers for you.
1. You get more char slots by unlocking them in the game. You unlock them by having pupil dojos make you their master.
2. You can't delete a single brute, only a whole dojo.
3. Not sure what you mean by is the pupil system the same, but probably the answer is no. Brutes don't pupil brutes, dojos pupil dojos. So you can only have one dojo per iphone and everyone pupils your dojo. When the pupil brutes level, all your brutes gain 1 xp.
4. Fights are renewed 24 hours after you last played the game.
5. The point of new arenas is the same as the point of more customization. Pretty pretty!
6. Yes, bears' stats differ quite a lot. There are pandas, which are agile but do little damage, grizzlies which are like normal bears, bear cubs which are tough but not agile, and polar bears which are tough but do less damage than grizzlies.
7. I'm not sure what all the possible pet combinations are, but you can only have one bear (as far as I've seen), two wolf and/or panthers, and three dogs. You can have any mix of bears and wolves and panthers. There might be an upper limit on the total number of pets but in general pets are VERY VERY COMMON almost every brute over level 10 has more than one.
8. Find your dojo master code by going to the dojo screen and tapping the mailbox icon. You will see a pre-written email with the code inside it.
9. Joining a master gives you great benefits. It gives you three days of double XP, and it gives you a second focus power (bear, snake, cat). The two focus powers stack, so you can get double benefits from bear/bear or snake/snake.
If you want to try it out, make me your master: DHFDFIFE is my code, the dojo is named dragonsfoot and it is Bear.