When an Elephant charges a unit in the flank, the unit only has to make one Disorder Save.

Using missile weapons while riding an Elephant:

The Beast-Master on an Elephant has a normal forward field, so he fires just like a normal unit; measure from the forward edge of the Elephant's base.

Lore of the Beasts:

Since the Beloved of Sobek is considered a Monster on the battlefield, the Beast-Master's "Lore of the Beasts" ability does work on the Beloved.