LTM4653 max duty cycle

1) We need to use this part in a 50V input to variable voltage(36V till 48V)/4A output configuration. From the datasheet its not specifically clear as to what is the min drop out voltage, or the max output that can be attained at this current (it talks of max output of 0.94Vin at 0A). Kindly advise. If its not possible here, please suggest any other Analog part that can do this.

2) What is the difference between EY#PBF and IY#PBF parts?