When is it good to break with c5 in King's Indian defence?


Only ...e5 is the true King's Indian Defense. ...c5 is more a Benoni Defense.
Only if White answers d4-d5.
Benonis are characterized by White Pawn on d5 vs Black Pawn on d6.
It is normally correct to play c5 instead of e5 when White has misplaced his c1-Bishop.