Hello I’m thinking in a game that involves the creation of a crowd, many characters on scene with their respective animations.
To have an idea imagine a concert. This involve to have many many characters jumping and moving enjoying the concert.
The question is how many characters could I have in unity if I target ios devices.
Thanks 
There is no real answer, the real amount of people displayed will depends how otimized you can, and how quality do you want.
If each character is a different model and cause one drawcall, probably you will have problems with more that 100 guys. If you change your model and texture to use dynamic batching, I think that you can have more that 1000 guys.
If you create everybody in an single low resolution mesh, uses the camera angle and position to cut some vertices, I think that you can get more that you need.
Benchmark different approachs and try to compare each otimization, after some cicles you will got there.