A lot of characters are limited as different stars. There's not many 1*, new 2* are rare. Usually when a character is added, they go into the 3, 4, 5, and 6* crystals (sometimes featured first) and there are older character who are not available as 5*. And some of those that aren't available as 5* are available as 6*. Right now, the 6* pool is a lot smaller because they add them slowly.
Comments
No only upto 4*
No.