Can anyone explain exactly what is the difference betw Rank S and Other Ranks. Because i quite didn’t understand, i compared Attack, Defence, etc… but every rank is the same. So what’s the different?
Moved to FAQ, the place where you should ask questions related to the game that have definite, clear answers (unlike questions that ask for opinions, for example).
To answer your question, the rank only affects the chance of scoring a bonus action. Rank S offers a 20% chance, rank A offers an 11% chance, and it goes down to 1% which is E.
Tks 
Can i ask one more question? what is Stars of the monster used for?
The stars are used of some kind of mark of quality of the monster, in most chases more stars means better stats
It also adds to the rarity of it as well
Though the starters are 2* and the hatchlings are 2.5*
I’d say don’t judge an arkadion by its stars unless it’s the final evo.