I've been searching through the menus to see if there's any description on the field special abilities of each character. I couldn't find anything. I looked through the posts and other pages to this site and couldn't find anything about the controls either. I can't figure out how to make Jean turn into a giant frog on the map. 

In the Guild Hall in Havenshire it will explain every character ability and which buttons to press to activate them. Also a pop-up on the world map is supposed to happen (I'll double check the bug) when someone joins your party  (Sorry the tutorials are not in the game yet).

Page Up:  Rand turns into a ball on the road.

Page Down: Jean turns to a frog on a beach (this is different how it works in the original game) to swim in the water.

Shift: Nina/Mina to turn into a bird.

Rand and Jean act differently than the original game. Rand travels fast on the dirt road on the world map without running into things and getting into combat.  Jean also cannot go on land now, but instead gives you access to the water earlier (vs the whale).